I was looking at them recently but decided against them. A decent one is a lot more expensive to a similar spec desktop, I couldnt really see the point in a touch screen as who sits close enough to a computer monitor to touch it. No upgrade possibilities really either.
I have a Lenovo 21.5 inch HD screen, 1 TB HDD, big i5 chip, touchscreen, etc. and it is as said the bollocks. People moan about upgrading, but hey it is no different from owning a laptop at the end of the day, you just renew a couple of years or so down the line. I got mine in Tottenham Court Road for £770 two weeks ago, so hardly expensive either. Would recommend these machines to anyone.