I called my local curries megastore and they said they received two lorries full, about 2000. As of this afternoon they have sold about 3/4 of them.
I don't really know what you mean about bad upgrade over the iPad 2 though ? There's hardly anything else for them to add on. It's got a massive update to the retina display, it's got a far superior camera, twice the ram, and a much upgraded A5 processor now with quad core GPU, 4G LTE radio chip and a battery almost twice as large. The only thing left for them to update this iteration is the front camera and the body.
edit:
So I just went and took a look at one. The thing was setup like crap. It was on a 3 foot high table and bolted totally down. I'm 6ft 3.. so judging the screen was kind of hard from that distance away - but it did look nice from what I could tell. Text heavy web pages were a treat - though from that distance the difference wasn't huge compared to the iPad 2 next too it. I bent down closer to it quickly to a normal distance and it was more obvious, though I didn't stay there for more than a few seconds as I looked like a fool.
You couldn't rotate it horizontally either, so watching 1080P videos on youtube was kind of pointless because it was in portrait mode and had a 3" black bar above and below it. They had none of the new retina enabled apps either.
So all in all whoever sets the Apple counter up at my local currys megastore should be fired.