Well, after having used reagents I have found that for most things so use it to more or less implement CML anyway. I have never been limited by the CML way, but I do appreciate the power that reagents give you.

In comparing STM and reagents I will probably just regurgitate what Aaron Turin says in his paper "Reagents: Expressing and Composing Fine-grained Concurrency" which you can find using a short Google. I only seem to be able to copy the Google link, so you will have to Google it yourself.