Has the Free Will Theorem of Conway and Kochen been taken seriously by the philosophical community? Is compatibilism still considered a valid approach to free will?
That theorem (overview) is often taken out of context. His suggestive naming of the behavior or elementary particles as "free will" irked a lot of people, especially as the connection to what we consider free will is phenomenally vague. It's almost akin to noting that Heisenberg Uncertainty suggests a lack of determinism (for the more quantum-mechanically literate, look into Bell's Theorem).
So the theorem is taken very seriously, but not necessarily having anything to do with what we consider free will.
Mixedmath's answer is a good one. I'd also like to add this supplementary data from a physicist point of view. As Sheldon Goldstein said: "We point out that for stochastic models this conclusion is not correct, while for deterministic models it is not new."
Besides, even if you stick to the non-compatiblist world view there are other points to be made for freewill than just indeterminism. I've written a bastardised argument in my blog for a general target audience.