I will happily compare it favorably vs the iPad for two simple reasons. 1. Better screen for what I'll be using it for and 2. more open and thus easier to make it work the way I want a tablet to work.
Will it outsell the iPad? No. To want this device more than an iPad? Very much so.
I suppose there might prove to be a few problems there that may ultimately end up delaying its release, or worse, killing it altogether.