I'm having some similar issues since upgrading at end of November (and getting my 1 year service). For the most part, 10 is an awesome upgrade! I love the throttle blips and the gear shifts feel MUCH better than the prior version (mine was 8.3, I believe). They don't feel so mushy when upshifting, which was my biggest complaint for the prior update. Nav is pretty nice once you figure it out. The issues I've had are:
- Multiple (four so far) lockups of the audio portion of Iris at start up. No radio, iPod, etc, Sometimes the Nav still functions, though. Radio and iPod are non responsive. Other times the screen does not repond to any button presses. Almost every time this has coincided with me removing my iPod when returning home and plugging it back in before leaving. Might be entirely coincidental as it doesn't seem to happen every time, after testing that theory.
- One reboot of Iris while driving. A little disconcerting, but at least the car kept going!

- While the car warms up (from a "bone-chilling" southern California 40 degrees F

) the radio and iPod audio snap, crackle and pop significantly. The problem decays over time until it is only a mild, occassional crackling after about 15 minutes. Subtle drop out of audio still occurs. I was having this problem a little before the upgrade and I resampled all of my iTunes music with a lossless compression. That improved the audio a little, but dropouts still occurred. I was hoping the update would fix it, but since then it has increased significantly.
- About 25 to 30% of the time when the car is cold and I just start to pull away (forward or reverse), the parking brake will unexpectedly reengage for no reason and the car will jolt to a stop. This only occurs within a few minutes of the car starting up (not after it has been moving for a minute or twos) but sometimes it happens many times. At one point after 5 attempts to move the car and jolting to a stop I thought it just wasn't going to go, but eventually it did.
- Got one random "Tire Monitoring Fault. Call McLaren Service Center." warning. Hasn't occurred since then.
Overall I like the update, but after a track day next weekend I'm going to bring it in to see if there are unrelated and/or fixable issues at play. It's very difficult to give it up while it's in the shop, though! 6100 miles and counting....
John