You're probably better off getting a PS4 or upgrading your PC. SSD is a short term fix and with more emphasis being focused on next-gen gaming PS3 user could potentially be left in the dust. If you can't wait 3 months for the PS4 release then SSD can give a small but noticeable increase to frame rates and load times.

I'm on PS3 and currently nothing in the game would make my experience "game-breaking", other than attempting speed runs but idc about those. It really depends on your ISP. My buddy is on a PC and I get much less lag than him due to him living on the west coast and I'm central.