Hi, my issue is a minor one but also something I wouldn't mind sorting out.
I've had my Nexus 7 for a couple of days and I am extremely pleased with it for the most part, I only have one minor issue, YouTube occasionally stutters, the stutters only last for a fraction of a second so it isn't a major issue, but it is a tad annoying. I have updated the device to Android 4.2.1 and the Youtube app is 4.1.23A.
It likely has to do with the wireless signal sometimes it fades a bit. Also data transmitted wireless is not always at a fixed rate. It varies from moment to moment sometimes data transfer is faster than normal, sometimes it is slower than normal.
This is partially due to the signal strength, the sensitivity of your phone's antenna and the speed at which the data is being received / transmitted. It's more or less out of your control and is normal for wireless devices.