You just have to read the threads over on the GAF to realise that Kinect in many ways works much better then people expected and although I think everyone acknowledges 'some lag' if you look for it, to most it isn't detracting from the experience. It still is at the moment aimed purely at the casual crowd, so until something more relevant comes out, unless you want Dance Central, or are buying it for the kids etc, It's best to just ignore it.
With lag, the biggest issue is as has been highlighted by places like digital foundry, even if it was 150ms (comparable to 30fps FPS games), it would still feel much more laggy if you look for it since it's amplified by the fact your body has lag in it (from the time you want to raise your arm, to it actually getting there is inherently a few hundred milliseconds), and mirroring the motion in your avatar gives you unprecendented 'lag' feedback.
I also just realised the other day, my Main TV (Toshiba) had horrific lag, which I only spotted when I was playing Fable II 'jobs' and seemed to struggle, I just hadn't noticed the lag in the rest of the games control mechanics, switching the TV to 'game' mode and the lag is greatly reduced.. I reckon a good 150-200ms extra lag was evident before, that alone with Kinect + it's own lag would amount to 400ms or so, something even a blind man would notice.. My PC monitor has almost no lag whatsoever, so if I do get Kinect and want to really analyse 'lag', I'll use that to see how bad it is..
But then when it's actually tested, it seems it's just an incorrect bandwagon people are jumping on..
http://www.computerandvideogames.com/article.php?id=274158
Not sure why I keep defending something even I have little interest in, other then something to buy for the kids... LOL
i only placed my order with a well know high street (online divsion) store and i just spoke to them and they said they have loads in stock 