If they wanna see lag, get a OG Droid on 2.0 and compare it to the G Nex. (what my OG is on right now, all I could sbf back to to fix the phone) I had a G Nex, and lag wasnt on of my worries. WP7 is just nicer with the UI speed and movement. Nicer than the iPhone, IMO.
It may not be the best at being non laggy, but it certainly isnt the worse. And its better at it than stock Android on phones before ICS. At the same time, the RAZR I have, with a skin on top of Android, an older version of Android, is just as nice as the G Nex as far as lag. (also hard to compare older stock versions of Android, I dont think any had similar hardware to the G Nex.) And does the screen res play a part? Just asking, dont really know.
My vote non existent "issue"