Obviously, we have an interesting view on this whole problem. I'm personally of the opinion that PaaS is still not quite the right solution - there's certainly some progress, but there's such an murky boundary between what a platform and an app provides that it's hard to make something that doesn't surprise people in some way.
It's interesting to note that as a PaaS platform you do get an advantage over IaaS - you can share resources and box-pack apps a lot more efficiently when you control memory and disk access at that higher level, so it's not like IaaS is certain to win either.
I probably need to compose my thoughts into something more intelligible and write a full blog post about how I think deployment should evolve, but I have a migration to shepherd first.