I think it'll be a success, but I can't think of a reason to own it other than the MLB app.
And I think I've already decided to pay for Extra Innings as opposed to mlb.tv or a mobile app. I can always watch from my laptop via slingplayer.
Would I rather have it than a Kindle or Sony reader? Hell, yeah. But it's still a bit short on features (no camera = limited skype, no multitasking, Safari only = bad news for those who must use badly-designed web sites for work).
What do you call something that doesn't FAIL but doesn't WIN, either?
ETA:
Ironically I would have been more interested if this had actually turned out to be a "Mac Tablet." Compared to a Kindle or netbook, though, this thing compares much more favorably...