Crackberry's very extensive review:
http://crackberry.com/blackberry-playbook-review-official
I haven't read it yet. I imagine this one will be more biased towards RIM, but it looks to be fairly in-depth so I imagine it will be quite a useful review.
Edit:
Documents To Go Premium versions are included free on the playbook for those that are into the office productivity stuff.
The crackberry review doesn't seem biased, he hits on the same points as the others. Basically saying if you're not a blackberry user, wait.