This is the first Beta of FF3 that I have tried. Reports on previous ones liked the speed but disliked the predictable lack of stability.

Initial impressions are that not much has changed on the UI side apart from some of the action buttons etc. I've read a lot about design concepts for V3 and it doesn't look like many of them have made it through.

I have to assume the download manager is not finished since it is denuded of icons or actions and only has right-click context. I have not had the opportunity to try it's new restart features.

The biggest gain (and it's a huge one) is in speed, particularly on JS heavy sites. I don't know if I'll be able to go back to V2 after seeing how slick this beta is with GMail. It races along with minimal delay on clicking most things. Is it pre-loading/caching lots of stuff?

I've seen a few display glitches but nothing too serious so far.

Most of the mainstream plugins seem to have been ported already which is excellent but there have been a few regressions from Beta 3 to Beta 4.

There isn't really much else to say. I know that lots has changed under the hood but so far it's not the amazing leap forward that some were expecting.