I got FireFox not as happy as I thought I would be because I cannot notice anything that much faster. But I will still use it.
my rig: Foxconn M7VMX Series|Intel Core 2 Duo E7200GHz|2.00GB of RAM|500GB Western Digital SATA HDD|500GB Hitachi SATA|500GB Maxtor External|Nvidia GeForce 8 Serise 512MB.|400W power supply.|Windows Vista Ultimate|19" HD Monitor
Been using FF3 for a day now and the only bug I can see at the moment is when your organising your bookmarks, Alt+B then Ctrl+Shift+B. In the top left corner where you should have the forward and reverse buttons? They're not displayed properly.
And I can't seem to organise my bookmarks in name order.
So I might have to revert back to FF2 as it seems that FF3 is buggy, as to be expected.