In a nutshell, only the forums got hacked, not the Steam accounts themselves. They also don’t think any credit card information or other personal information was stolen.
That said, I’m monitoring my debit and credit cards a little more closely for the time being. I don’t know how many of the users here used Steam to get their Positech games (I do), but just want to spread the word so you guys won’t be featured on the next “F-R-E-E That Spell Free… Credit Report Dot Com Bay-Bee” ad. (Sorry for the non-US folks who don’t get the joke),
But I’ll repeat, there’s no evidence of credit information being stolen, but it doesn’t hurt to be careful.