I think obviously the big worry does come down to warranty, and therefore a UK distributor and good dealer support is going to help this.
I know that some people have bought these bikes direct from Germany but in the event of a problem, I personally wouldn't want to fuss about trying to talk to the Germans and wait while my bike has to be shipped there and back etc. If it was sold properly over here then this could be sorted out on the spot!
As for frames cracking/snapping, we have very few entering our shop these days. But that said if I was spending 2-5K on a bike I would not want the worry in the back of my mind.
Back to buying a bike from Germany, its all well and good reading reviews/looking at pictures but I think its best to visit a dealer and see/touch/feel/ride the bike...
Saying that there's a nice local woods to my shop so I may end up taking a few people out for a ride on the Haibike's, when the time comes. A good 10 miler round trip with some rough stuff in between, who's game?
Martin