keyplyr - 10:49 pm on Feb 18, 2012 (gmt 0)
Most linux/ubantu/jaunty users will hang on to the last stable build for at least a year or so. That's just the way that community is. Just a few months ago I surveyed (via the linux newsletter mailing list) and this was the overwhelming response.
I too had tried blocking /3* for a couple weeks across several sites and found I was stopping a huge amount of legit users when I physically followed up on every 403.
Yes there are always malevolent hits coming in with the FF/3.0* UA, but, as you said, I block them with other rules.