SBCL is rock-solid, fast, and easy to use. It's compatable with everything I throw at it, and best of all can be kicked into the right shape for deployment. It has some advanced options that not everyone will always need, but are such a boon when you do. I had an entire project that wouldn't have gotten off the ground if it weren't for their "merge core pages" optimizations. Good work guys!
As good as any huge CL system, no better.
There are no 4 star reviews.