Apologies Moderator - I started this new thread by mistake. I thought I was adding the above post to the 'Firefox 2 beta' thread. Not sure how that happened. Sorry.
It's not ready for general use as yet. I've come across one bug myself so far (an embedded video won't play in the beta that will play in 1.5) but there are probably others. Also, most extensions don't work unless their version numbers are updated. This can be done either manually, or automatically by using the 'Mr Tech Local Install' extension. Updating the extension version numbers doesn't always work but it mostly does.
Firefox 2.0 beta 1 (Bon Echo) can be tested at the same time as keeping Firefox 1.5 as your main browser. Creating a seperate Profile will be necessary for use with the beta version though. This affects the way that Firefox 1.5 starts up (the correct Profile needs selecting from the Profile Manager). It is possible to run Beta 1 entirely independently of 1.5 but this takes a bit of setting up using a couple of .bat files.
I found Beta 1 didn't seem to like something about the Profile I'd been using for the Alpha 3 version of Firefox 2.0. Rather than try and find the actual fault, I created a new Profile for it. It seems to be working OK now apart for me apart from the video problem mentioned. Also found that when beta 1 was first installed and started, it grabbed hold of the 1.5 Profile and disabled all my extension. However, once Beta 1 had its own Profile, the 1.5 extensions could be re-enabled again and all was well with 1.5 once more.
In short, whether you install it or not depends on if you think you would enjoy testing a beta release in order to get a preview of it and see how it works. Be prepared to come across some bugs and a few difficulties though (or they can seem difficult if treading new ground). Also be aware that the beta may, initially, upset the working of 1.5 (remember the extensions problem).
If you just want a browser to use, it's probably best to stick with the latest official release of Firefox 188.8.131.52 as has already been advised.