Version-less updates of browsers makes sense, and they should be seamlessly, silently, updated in the back-ground. This is getting crazy.
I install Firefox for friends and family who I want off IE, and this actually embarrasses me a little. If I have to keep telling them to update, they will quit - or end up using REALLY OLD versions of Firefox and we'll have an IE6 situation all over again soon but with Firefox.
I'm starting to install Chrome now. At least I can say that their browser will always update, and they have nothing to worry about.
The upgrade to 5 isn't much different than going from 3.8 to 3.16. Mainly, they've changed their numbering scheme, so there's no reason to make a big deal about it.
Here's the about Firefox dialog http://i.imgur.com/cDbN1.png and the update request http://i.imgur.com/4SYRI.png