Going forward I'm planning to dedicate a chunk of my mornings to working on Nimbus, splitting my time between going over pull requests and building new features. I love building tools to accelerate the development process of other iOS developers and plan to continue doing so for the foreseeable future.
I'm sure you're telling the truth, but the fact that you feel you should mention it speaks volumes about Facebook & the reputations we cultivate.
Of course a better iPad experience comes from an app designed for that form factor but there's nothing to stop you releasing one version and then iterating on it.
So one can quite reasonably argue that Facebook has been holding back the iPad app, which raises the question of why.
I can't believe Apple doesn't want this app released given the popularity of Facebook. The original version of Ping was also integrated with Facebook that was pulled at the last minute due to "onerous terms" [1] (according to Steve Jobs).
The prima facie evidence is that there is some kind of tussle going on between Apple and Facebook. Perhaps Facebook's "onerous" terms included demands on the iTunes service and Facebook integration (which is lent more credence given Facebook's recent moves into music)? Perhaps Facebook wanted Facebook login to iTunes and other Apple properties? I don't know.
What I suspect is the iPad app is another bargaining chip.
To argue it's not "feature complete" is disingenuous. This is a subjective measure of simply deciding "that's enough".
This is not to say that your conclusion is incorrect, but unless something significant has changed with Three20 since the last time I used it, it isn't super-usable on iPad.
I also really want to emphasize that my time at Facebook was incredible and my reasons for moving on were remarkably complex, none having to do with any dislike for Facebook or ill feelings. The number of hours I put into the project were out of genuine passion for the product, not because anyone was forcing me to do so.