Most of them are changing to high penalty APRs, I have a card with a balance of $450 out of $7000 and they sent the same letter you got last week.
I've started using my AMEX Gold for everything, granted it's not a revolving line of credit (full pay off required each month), but it seems to have the best rewards and the best discounts on hotels/travel etc. It's 1 point per dollar, so it adds up fast. If you get the premier rewards you get 3x for airfare, 2x for gas I think, and 1x for all other purchases. Higher annual fee, but better perks.
I started typing out all of the cards I have just now and it's depressing. brb suicide. I have like 9 credit cards. wtf.
I am pretty happy with first national, first they bumped my rate by 2% and I bitched at them, then moved the funds off of the card.. They sent me a 7.99% lifetime APR, no fee on a balance transfer offer. Pretty good deal I guess.
Keep in mind when you do a balance transfer that amount generally doesn't count as rewards so you won't benefit from that portion of it.
Discover is a bunch of idiots, I've never had one but they offer me one once or twice a month, I've tried to accept their offers twice now in the past few years and they say oh sorry.. then 3 days later they let me know i'm approved. Idiots.