If you're from a BMX background and intend to do tricks, I'd look into some of the bikes now being put out by BMX framebuilders. There's BMW (I think) and some other frame (look at the Interbike thread, I'm sure it'll be a recognizable name). Anyway, they're a slight bit heavier, but have a more track style geometry than a conversion and the tubing is oftentimes the same as for their BMX frames so you can do all that crazy **** I know you BMX kids do.

Other than that, I'd look into trying to find a setup with 36h wheels and possibly a stronger V section rim. Have fun with it. Some friends of mine got into it and after destroying countless forks just screwing around, they are now trying to squeeze me off my turf (road riding). Not that it's a bad thing but you folks tend to do all the neat tricks with half the effort, then you want to ride 50 miles at 22mph. It's unfair.