Sales are disappointing, sure. It's readily available, it's in no danger of selling out. I would, however, say that Europe is expected because it just hasn't been pushed, and aa far as the UK goes, isn't even stocked in many branches of the biggest gaming retailers (supermarkets). Really odd / foolish strategy on Nintendo's part.
However, people forget just how mediocre HD sales in general were post-launch and pre-price drops last time around. If the supply is there, I would expect at least one of the other two to launch stronger than Wii U (I reckon that the other will be a comparative dud and if it sells respectably, it'll be through attrition ala PS3) but taper off even more significantly until the price begins to slide.
Of course, if we get a shock > $300 launch, that changes everything.