According to Joystiq it is safe to resume gaming. Here is a quick faq from joystiq to help you all relax from your MW2 withdrawl.
Q. Is it safe to turn on my PS3 now?
A. Right now, it appears the answer is “yes.” The PlayStation Network is online and fully functional for owners of the PS3 Phat system, and games appear to be running problem-free. Sony has yet to issue an official “you can use your PS3” statement, however.
Q. Do I have to download a firmware update?
A. Nope. The problem should just fix itself automatically, whether you’re online or not.
Q. My Trophy data for [insert game here] is gone! (I know, I know — that’s not a question, but still!)
A. If you lost any Trophy data over the past 24 hours, there may be a way to salvage it. Launch the game for which you’re trying to restore Trophies and it should automatically recreate a Trophy data set on your PS3’s memory, which you can then sync with the PSN server (just by opening up your Trophy list in the XMB). Our Heavy Rain Trophies had vanished, but this trick brought them back from the ether.
Q. The time and date on my PS3 are wrong. How do I fix this?
A. Under Settings in the XMB, then under the Time/Date settings, you should be able to set your console to automatically sync the time and date via the internet.
I know it was a rough day or so, but don’t run out and sell your PS3 unless you were already planning to do so. Hopefully Sony learns from its mistake and slew of angry customers and this incident or any other like it never happens again.