I am a web dev that has been using Ubuntu as my desktop host OS since version 6.06, and I'll be the first to admit that, while 10.10 is a significant improvement, there are still some problems that probably keep it from being mainstream.

One example: I currently use an ASUS laptop. Every time I get a kernel upgrade from Ubuntu, it breaks my Nvidia driver so X server will no longer start up properly. So I have to go into the shell, stop GDM, start the Nvidia driver install (I keep a local copy just for this), and then restart GDM.

It's just a minor inconvenience for me, but the average user is going to lose his mind when the computer appears to fail at bootup.

I still use it because I find it to be the most productive environment for my work - it gets in my way far less than any other OS I've tried. But, yes, there are a lot of hardware-related problems that still haven't been dealt with. I suspect there will always be.