Congrats on the relaunch of the launch! I was trying things out today and came across some issues. The first category of those installation issues:
1) I visited the site with my old version (2.0?) and got the error "BrowserPlus failed to initialize." The problem was "bpPlugin.unapprovedDomain: undefined" It seems like the JS include would be able to handle running an older pre-installed version.
2) Finding an install page wasn't too hard (Support page), but if a forced upgrade was necessary, I'd expect that to be a bit more obvious. After going to the install page I got a clear indication of the error, though it might have detected an older version and suggested having me download the version for my platform rather than making choose between two links for mac or pc.
3) I suppose platform self-update failed since I got an initialization error rather than a prompt to self-update. Also, since I had to re-install via the support page rather than auto-update I had to restart my browser(s) to get them to recognize the new plugin. (could be a JS error, or maybe just a by-product of manual upgrade).
After going to the support page, doing a new install, then restart all browsers, things were fine (10.5 Leopard, Safari 3.1.1 and FF 3.0)