I have not yet used the CLR. As Grant mentioned I would bet more people on 2008 are if you include the Spatial and Hierarchy data types which are CLR types.

The reason I don't use the CLR is simple. I haven't had a task where I found it to be necessary. I don't work on big, high transaction systems where milking the a few milliseconds or even seconds of performance is necessary so the time needed to optimize to that level is better used elsewhere. Before I get flamed for saying that, I do attempt to write the best-performing code I can, but I don't have to seek out faster solutions if the customer (end-user) is satisfied.