For those of you who have Steam Guard enabled, I'd recommend deauthing all pc's - just in case:
Steam > Settings > Manage Steam Guard Account Security > Deauthorize all computers now

Unlike the PSN (info stored in plaintext), passwords have been hashed/salted and credit card info has been encrypted.

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http://forums.steampowered.com/forums/

"We don’t have evidence of credit card misuse at this time. Nonetheless you should watch your credit card activity and statements closely."

"If you have used your Steam forum password on other accounts you should change those passwords as well."

ANDYZ0r, updates on new site?