I updated a couple of hours ago. I run Windows XP. It's too soon to tell how much of an improvement the new version is, but I can tell you that Firefox's automatic update feature--new to Version 1.5--worked slick as goose-grease. Previous to 1.5, upgrading required shutting down Firefox and every other running program, then installing Firefox as though it were a new program. But the upgrade to 184.108.40.206 happened in the background, without any trouble, while I continued to work in other applications in the foreground. Firefox even shut down by itself and re-started automatically.
Some Firefox extensions that are compatible with 1.5 are not compatible with 220.127.116.11, so I lost the use of LiveLines. I hope there's a 18.104.22.168-compatible version of Livelines soon.