I had an 8120 in my WRX before I got the accord, overall it was ok, but if you consider price to performance it just wasn't there. The kenwood radio tuner sucked dog balls, having to continuously pay for navtraffic sucked($120 and I'll never pay for traffic updates again with MSN), overall the screen was pretty blah(although I did like that you can adjust the color settings, not just brightness), dual zone was nice, but I only plan on single screen in the accord, the bluetooth stack was terrible regardless of what phone you use(the F90 doesn't particularly like my HTC phones though), I love ipod VR on the F90, A2DP was decent on the 8120(but not great quality, bluetooth stack again), the EQ is much better on the 8120 though. Have you tried skipping songs on a USB drive on the 8120? All in all I guess it depends what you want. After some tweaking I'm pretty content with my F90.
I'm curious how your ipod was locking up. My 8120 forgot it had XM far more often than the F90 forgets it has an ipod. The only problem I've seen is with bad songs if you ummm download a corrupt one, and if you turn the key to accessory, sit for a few seconds and then start the car. It's the ipod that actually freaks out, not the AVIC. I suppose in order to speed up boot time there isn't much delay between when you turn the key and the avic inits the ipod. When you start the car the ipod tries to reconnect, but it just sits there instead. The easiest way around it is to stick the key in and start the car.