I'm currently having my manuscript critiqued by two members of Deadly Prose, an exclusive critique group designed for novel length manuscripts that requires tests of both your writing and critiquing skills before you can be admitted. As the testing implies, it's a moderated group.
There's a serious advantage to moderated groups when you're critiquing a whole novel at once. With single chapters and short stories, you could critique one, then if someone responded with a helpful critique of your work you could do another, and so on. A novel is a bit long to critique only to discover the other person has lost interest or is unhelpful. Besides, you may not need a novel critiqued at the same time as anyone else.
Deadly Prose operates on credits - and has rather strict formatting rules for quality control. You don't usually get to choose who critiques your manuscript. The moderator (thank you John Darrin!) does try to make sure you get value for your credits, but there's still some luck involved. And it takes longer because three humans are involved in every transaction.
On the other hand, this is one of the few ways to make sure your entire novel gets critiqued. For books like mine, it would be very hard to provide a useful critique of the final chapters without having read the rest.
Have you done whole novel critiques, or had them?