Yes, it is a joke, but FF is the only browser I'm fully comfortable with. I've given the other main contenders good trials, but I always end up bumping into some little niggle which I can't work around. Usually it's font handling or smooth scrolling.
There shouldn't be an issue with addon incompatibility, because Mozilla guaranteed a little while back that the addon API wouldn't change from v4, so addons would continue to work with later versions. The problem is that addons have a configuration file which specifies the min and max versions of FF that the addon will work with. If the addon author hasn't updated this file, then the addon will stop working when FF gets beyond the specified max version. In most cases you should be able to edit this file to make the addon work.
The configuration file is called install.rdf in the Linux version, and I guess it's the same for Windows. Each addon has its own folder with its own version of install.rdf. The section to edit looks like this:
<!-- Firefox -->
<em:targetApplication>
<Description>
<em:id>{ec8030f7-c20a-464f-9b0e-13a3a9e97384}</em:id>
<em:minVersion>3.0</em:minVersion>
<em:maxVersion>6.*</em:maxVersion>
</Description>
</em:targetApplication>
You'll see I've changed the maxVersion value (between the > and <) to 6.* so this addon will now work for all 6.x versions.
I've done this with a couple of addons, and all the ones I use now work.