As cool as Google Voice's free text message service is, it has always been a bit barebones. Big features like MMS have been missing for a lot of users, with some notable exceptions. Multimedia Message Service, usually used to simply attach a photo to a text message, is handled by completely different servers at most carriers, causing some problems with Google's forwarding system. It looks like Google has addressed these issues, at least for most people in the US and Canada, finally enabling the sending and receiving of MMS via Google Voice.
Google employee Alex Wiesen announced the new feature on his personal Google+ account.