the harry potter set is the Bachman EZ track, and that is a hundred times better vareity wise then the life-like style track of the disney world train set ( i think its snap-loc or something along those lines). the problem with the ez-track and others is that the railed don't smoothly but up with one another where they connect, among other weird issues. Maybe you haven't had problems yet, but its certainly a problem for alot of people i've talked to. additionally, their switches and things cause a billion and one different derailements. I'm not sure where the problem is to fix this, but every once in the while, (usually the second or third car in my passenger consists) will diverge onto one of my #6 crossovers when going through it, even though i repeatedly check to make sure the points are lined up and all of that. its very frustrating. as for steel rail... i have it on my layout, and its usually not a problem. I do notice my steal EZ track gets dirtier faster with black grime and grease stuffs, but as far as corrosion goes, there is very little corrosion on my steal tracks. Brass track is the only track that seems to get dull and corroded any more than any other section of track i have, and even then brass track doesn't give me any problems. I always wonder why people freak out about brass track so much.