There's already six games announced that use this? How many Motion+ games were announced when it was revealed? Two? It's clear that third parties want to support this and it was a big oversight on Nintendo's part to not have one in the first place (not that I'm surprised; Nintendo thinks "gimmick first" these days.)
The requirement of a AAA battery is really lame. But it requires power and adding a rechargable battery was probably too expensive. The whole thing is shoehorned in in the first place. The position of it is dumb, the way it bulks up the system is dumb, so the battery requirement just fits the panicky amateur hour design.
The 3DS redesign is inevitable. It was anyway but it's going to show up much sooner than we figured.
Gotta love how Nintendo talks big about being third party friendly with the Wii U. Well, did you guys talk to third parties at all about the 3DS? You figure this "you need a second analog stick" would have come up if you did. Nintendo talks about winning back core gamers with the Wii U but 2011 has just been a massive "we-have-no-idea-what-we're-doing" clusterfuck.
Although there are similarities between this and Motion+, they're also vastly different situations. The biggest difference is that M+ came about pretty late in the Wii's life, and after most everybody already had the system. This has a much smaller established user base, comprised primarily of the kind of people who could be talked into buying one. It's a lot more realistic to turn this into something that's widely used than making M+ the standard ever was.
Also, this is less drastic in how it changes controls than M+ was. M+ required a vastly different way of motion control, and was basically either-or with the standard Wii remote, which limited its use to games more or less built specifically for it. As Crimm pointed out, this is easy enough to include as an option in games that also work without it, which means it's fairly likely that more games will include support for it. You don't get to be the standard by dramatically improving a select few games, you do it by offering a modest but noticeable improvement to a whole bunch of things, and this has the potential to do that, if enough companies get behind it.