EF as a whole is too heavy a load compared to nHibernate,

Coming to nHibernate from the MS world, people may be dismayed at obsolete documentation and counterintuitive stuff- even down to figuring out what version to install. ;-)

with EFs POCO, the discipline it gives us is almost the same

Seems sort of like a re-invented typed dataset to me. ;-) OK, I'm being cheeky... it's a lot more than that and it's great to see the EF making a better job of passing stuff between layers without needing a mighty steamship in attendance. ;-) Also I see it offers virtual as well as snapshot change tracking. Virtual means it's constantly updated and managed, but to me that feels a bit like something Borland used to do... great for demos but has to be heavy on resources. I guess we'll see.

The other impression I get is that while you can use SP with nHibernate (and with EF4 more easily than previous versions- something nobody seems to have wanted to talk about) it's still harder than it was with L2S from day 1. You had said you've used lots of views and SP, so what is your plan there?