It's not a bad use of miles. Comair Club is a very good product, and the SLOW lounge is perhaps the best Business lounge in the network. As someone else has said though, make sure you're on the left-hand side of the plane.

Equally though, 4 hours in Y with Comair is not unpleasant, and you still get a full meal, etc. If you're old enough, just imagine you're flying with BA 12 or so years ago and make your call.