I'm not a fan of proprietary storage solutions, especially when they don't seem to be technically necessary (which is pretty much always). If Microsoft brings the price down closer to that of an off the shelf solid state drive, I might pick one up. But there's no way I'll pay $220 for one.
And, I find it somewhat disappointing that Microsoft is going this way. I've always associated them with being much more consumer friendly in terms of storage options. I suppose it's not so bad though, since there's enough storage in both systems to have a few games, at least, installed at any time. If they bring the price down over the next couple of years, maybe I'll give them a pass. If they're still trying to get $200 for this thing 2 years from now, I'll have to consider that a strike against Microsoft.