This is really nice, but I must say I would wait a month or so for the final release to come out. Many of the extensions are still in process for compatibility, and I had some problems when I install this (granted, this was a week or so ago).
I think 1.0 is going to be a good improvement, especially with RSS.
I've heard of this bug, it really needs fixing. There seems to be a conflict between Firefox and some firewall software and/or anti-virus software (some say Panda, some Zonealarm, etc).