Both the Alesis Studiodock and the Akai SynthStation 49 are $199 at Sweetwater (scroll down:
http://www.sweetwater.com/store/search.php?s=ipad) Looking forward to playing with both of them when they come in. I've been using the Synthstation app on my iPod for months now (a few drawbacks, but otherwise I like it quite a bit) and am looking to upgrade to the iPad later this year.
The only drawback to that is we'll have to get two: one for me and one for my wife. Then the kids will want to know where theirs are.
The funny thing about all this is (to me) is that Weds afternoon, I was having a discussion with my partner about what I expected to see from someone - if not at this show, then by summer - was a keyboard controller with full-size keys, etc. and a dock for the iPad. Ten minutes later, we saw the Ion version online. That led us to discussing what else we'd like to see and what could be coming. We came up with the idea of a device that the iPad could plug into with audio and MIDI I/O, etc. Lo and behold, that night the announcements from both Alesis and Akai really surprised us!
This sort of thing continually amazes me. Honestly, it's like when the first Tascam Portastudio came out, we were (frankly) shocked. Now that sort of thing seems quaint (and you youngsters roll your eyes at me), but as technology moves forward faster, the tools are getting more and more affordable, powerful and smaller. It's a very fun ride.
I will be very interested to see what the next year or two brings in the way of tablet computers that run Windows (yeah, I know) and how that impacts the price of musical programs for them. I would love to be able to run Live or the like on a piece of gear like the iPad/Studio Dock - and I'm sure I will.