I think people define lag differently. For me its anything the Xoom hesitates, whether it is a tap, a swipe, or anything.
The Xoom definitely has hesitations, and that is lag. Even someone before said that his Xoom has no lag, yet he knows it hesitates a bit when he turns it on for a while until it is ready to go. That is, to me, lag.
Look, I love my Xoom a lot, and am in the process of selling my ipad 2 in favor of the Xoom, but I can admit it can slow down sometimes.
You clearly don't believe some people have no lag. My job has me traveling a lot to our clients. Many of them show up at meetings with the iPad2. We invariably compare units. My XOOM wins on just about all fronts. Starting an app... my XOOM mostly wins, but it's always very close. Opening a large document... XOOM wins, no contest. Browsing internet pages... XOOM wins, no contest. Remind me where this lag is?
The time to screen switch when turning it on it's side is not "lag". It's pretty clear that's the intention of the designers. The sensors clearly work in real time because we can play games (with fantastic response) that rely on them. So clearly, it's not a case of not being able to recognize the turn quickly.
I can appreciate what the engineers had in mind for what I call the "Are you sure?" period before flipping the screen. I'm often on a plane and tip the unit momentarily to get something. Upon righting myself, my eyes can go directly to where I left off without watching the screen flip this way and that. This "intentional lag" makes total sense if you think of it as a user interface / screen tip issue, rather than simply comparing it to the iPad2. IMHO, too many people don't consider real world situations and how it should be done. Instead, all they think about is how the iPad does it, as if that's they defined how it should be done and it can't be done any other way. Ridiculous!
If you want to call something like the screen swap delay a "lag", explain exactly how it inconveniences the user. You may as well complain the XOOM doesn't come in white, because the iPad2 comes in white... therefore all tablets should come in white or they are clearly inferior.
As for anything else being a lag. I don't experience it. Not on any one of our XOOMs. The moment we swipe, the screen sweeps immediately with our finger. The moment we tap on an app, that app opens. It doesn't miss a swipe. It doesn't miss a tap. The only time I can get it to miss on either is if I speed up my swipe or tap to a truly ridiculous pace. Even then, at a ridiculously fast pace, the screen will sweep completely. Most of the time, though, it starts to sweep then halts and slips back to the screen I was on.
I'm attributing this to luck, because unlike yourself, I'm not ready to say everyone claiming a different experience is full of it.