I tried discussing the problems of the SDK on macrumors, but the RDF was far too strong there. 1) It's incompatible with the GPLv3 due to the fact that an end user can't load software on the device without paying Apple first. So developers will have to be very careful on what they port to the OSX touch platform.
2) It's one more unnecessary lock-in. There is no reason Apple needs to prohibit tinkering and installation outside of the iTMS since most people will use iTMS anyways.
3) No persistence, no undocumented API's, no accessories... Apple still keeps all the goodies to themselves.
4) Apple as the gatekeeper... I don't think I need to say why this is a problem.
5) $100/year just to load custom code onto a tethered iPhone. $300/year for in house apps.
And of course, this is on top of the fact that you are paying through the nose for the Apple way of life. You pay hundreds of dollars for the device and then you get the honor of paying every month for a locked in cell provider or pay for basic updates. Now you get to pay for every application that you install as well.