Hi Bob,
Welcome to large scale RR'ing! Your first answer is NO, not all track is interchangeable. Bachmann track is hollow and ONLY for indoor use. If put outside, it WILL rust, and quick. For outdoor layouts, you can use brass, aluminum, or stainless steel.
As for your engine, make sure you lube it. Bachmann makes a full line of oils and grease, but whatever you use, make sure it's plastic compatable.

Welcome and good luck

Brian,
nice job on them all! Do you have a garden RR in 7/8ths? My wife and I saw one during open house month last year in Del. This hobby never stops amazing me on how much you can do with an imagination and a supply of donor parts.
Congrats on your placings!

JD,
nice job on the weathering and the mod's to this engine. You should have given a seminar on weathering at the York show!

Brian,
Did you have a railtruck in the model contest? If so, very nice job! I was told by a friend that it was yours, but he didn't see you at the time to introduce us.

You are on the general question forum,
Since yours in specific to On30, click that link and you will get folks that are experienced in that scale.

Lee,
It was marketed as a 1:20.3 engine, but it was a small engine. I know alot of folks installed a larger cab to make the engine scale out to a more proper 1:20 scale proportion.

I too still keep my eye's open for one of these great little engines. None to be found at the ECLSTS this year. Believe it or not there were some older Climax's new in boxes at the show. So many things to look at and lots of running layouts to view and get ideas from.
They still pop up on ebay from time to time, but the price is much higher then when they were new.

Good luck

I'd still like to see a T-boiler in large scale

Joe,
Your tip on the siding makes really good sence! We have been thinking of adding on a third loop, and your tip would make the sidings work out well.
Thank you!

Kybaugh,
It really depends on how much you want to spend. Bachmann track is able to be picked up really cheap on ebay, and as long as you don't put it outside (or in a damp area) it's fine. We have a dehumidifier in the basement, and have never had rust issues. As for carrying current, I haven't had a problem and I've run it now for over 5 years. I am slowly collecting brass track for our future outdoor layout, but the steel track and all metal wheels has worked out fine for me. It also depends on how big of a train you wish to run, if you ever plan on getting a "K", you'll need much wider curves than what Bachmann offers.
If you are watching pennies and just plan on running a 10wheeler, 2 truck Shay, or Porter, you'll be fine with Bachmann track. But if you plan on getting into the larger 1:20.3 stuff, go with wider curves right from the start.

I have a suspended double track system in the basement. I use the factory Bachmann track. Since all Bachmann curves are the same, I just added some straight track on the width and length to allow them to pass without hitting. Bachmann track can be cut to come up with half lengths, but you have to be careful not to collapse the hollow track. I also soldered all the cut joints together from the underside.
I also added a siding on one side to park another train, and I learned a lesson with this. I used the Bachmann turnout going right, then connected a curve directly to it going left, the 10 wheelers can't handle that sharp "S" turn. The cars manage it, as well as the Porter, but if I want the 10 wheeler sitting there, I place it there for looks. I have that section of track insulated so power is not a concern.

Good luck

Tom,
In case you're not sure what I'm talking about with the track cleaner, you can take a look here:

http://cgi.ebay.com/BRITE-BLOK-TRACK-CLEANER-FOR-G-SCALE_W0QQitemZ120234214427QQihZ002QQcategoryZ19157QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

They do work nice!

Hi Tom and welcome to large scale,
I have an indoor layout using Bachmann track. Even though it's not the best, I have had no problems with it inside. I have two loops, the inner loop is 47ln ft, and the outer is 56 ln ft.
I've used a San Val track cleaner mounted under a caboose. I also made a cleaning car that uses a sponge that I mounted under a caboose and I just add on track cleaning fluid. No special brand, just cleaning fluid from the local hobby shop. The sponge is held in place with two dowel rods I pushed through the sides so it will stay in place.
I really don't use that one as much as the San Val unit. Of course now San Val is closing down, but you can still find the cleaning blocks on ebay

Good luck

There is no magic number that you are looking for. Different things will impact this, metal wheels vs plastic, curves (wider the better, so your plan is right on!), grade, condition of the engine, etc. Keeping your engine lubed is very important especially when running alot or pulling long loads.
I have a simple layout with almost no grade, and I pull 5 passenger cars with a stock Big Hauler. I don't run it for extended periods, and eventually when something does give way in the drive train, I'll be putting in a BBT drive complete with the new shorter front pilot wheels. But for now she just keeps chuggin' along. I can even run the smoke while pulling them without a drop in performance. However, we do have a very early series Big Hauler, and we have 4 cars behind it, a box car, gondola, tank car, and caboose, and it keeps going, but it's not happy. And if you turn on the smoke, forget it, you are'nt going anywhere fast.

Hope this helps!

Hi Bryan,
Have you ever owned a Shay before? The reason I ask is because Shays are geared locomotives, and even the real ones were slow. Bachmann has built them this way. If this is not your first Shay, then more info or sending it back may be in order, but if it IS your first Shay and you are used to rod engines, your Shay is doing what it's supposed to.

I don't believe trains are on their way out, but times are ALWAYS changing. When I was growing up, yes my Dad and I were into trains, and had multiple layouts in the basement. Then I started dating and trains were forgotten about for years. Years after that, I got married and guess what got me back into trains.....my wife! She had never had trains, but loved watching them, so one year we bought "her" a large scale B-mann set for under the tree. We now have numerous large scale trains, we have also gotten my dad back into the hobby which we both enjoyed growing up. The tides turned, he originally brought me in, now we returned the favor. It gives him and I a chance to spend time together. During open houses, and garden tours, my wife and I take him with us to visit other layouts, and I cherish this time I still have with my Dad.
As for the younger generation, like him or not, Thomas brings kids into this hobby. My nephew loves Thomas, he has been to Strasburg to actually ride behind him, and that also introduces him to the "real" trains of the past and present. He has a layout in his basement, and yes for now it's every Thomas train you can think of, but hopefully this will eventually lead to his first HO or O starter set (I don't think his mommy would go for large scale....). This year we will be taking him along with us on garden tours, so here we have re-introduced my dad (older generation), myself and wife (middle age), and our nephew (younger generation) to this hobby. 
The popularity of large scale right now (in my opinion) is growing very quickly. We we take garden tours, more and more people are joining in, and even using suspended systems in their homes (like we did for my dad).

So yes, things always change, but there are always some constants that always stay around, and thankfully in my eyes, trains are one of them!