Interesting that they let you in with that existing high util! I suppose it's possible that they could whip around and F/R you. Apparently the decision to F/R is done by a different department than the one that grants credit. It would be nice if they'd discuss this internally.
Anyway, your best bet is to use the new AmEx but pay it off immediately, never carrying a whisper of a balance. Until you get your first statement, you won't be able to pay on their site, but if you can do bill pay from your checking account, you can force payments into their unwilling hands.
In the meantime, they will likely soft your EX report at least every 15 days. The best advice I can give is to not allow any of your existing balances to increase; to keep paying them down by noticeable amounts (AmEx is looking for this); don't abuse your AmEx card in any way, shape or fashion, and keep your 2007 1040 form and your most recent pay stub handy.
BTW, the only inqs that are counting in your scoring are those from July 07 onward (the most recent 12 months' worth), although of course they do display for 24 months. Good luck!
* Credit is a wonderful servant, but a terrible master. * Who's the boss --you or your credit? FICO's: EQ 781 - TU 793 - EX 779 (from PSECU) - Done credit hunting; having fun with credit gardening. - EQ 590 on 5/14/2007