graeme_p - 6:35 am on Aug 18, 2011 (gmt 0)
@Fotiman, FF has run plugins out of process for more than a year, and that solves the major cause of tabs crashing.
It does tend to slow to a halt if left running for a long time - a day with heavy usage, more with light usage. My heavy usage is very heavy (20-30 tabs at a time, all day with 14 extension installed).
You do use more memory with process per tab, and I believe this is more of a problem with Windows than *nix OSes.