I used to get notifications of mass memory usage. As much as 4Gigs Every day it seemed like.
Turned off Hardware Acceleration where Applicable and haven't had a single notification since.
If you're getting barebones (happens occasionally) I think that's more a Flash issue than Browser issue. I get them occasionally but it's only one page of my 20+ pages that happens to while loading. I just let it go its course and it generally course corrects itself. Rarely do I have to refresh to fix it. If you're having this issue and it's not correcting itself check the Downloads section in OP to see that you have the correct version of Flash installed.
Not that it's gonna matter long cause FFox is on 16 now so there will probably be a new Waterfox soon.