I've been racing an NJS steel frameset over here with some pretty good success against riders on bikes many, many times the price. It's not the bike. Anyhow, it isn't really much heavier than many of the new type bikes. My teammate has an Anchor carbon bike and it's HEAVIER than my steel bike! Weight really isn't much of an issue on the track. Buy what you like.
Anecdote: I have a friend over here who recently upgraded to a Teschner form an older steel keirin frame. His difference in times? Nothing. In fact, his fastest 200 and kilo are still on the old "inferior" bike. Make of that what you will.
Additionally, if you can find a fair vendor, an ex-keirin frame is a good value. Frames are often retired on a yearly basis on principle, even if they are un-crashed. If you can find one of these it's basically new. Good luck!