C-Net gives Radio a pretty glowing review. It only talks about Radio as a blogging tool, but it's full of "I love" and "This is great" comments.

One comment. (italics mine)

The bad: No spelling checker; downloading software slows the setup; unattractive predesigned templates.

If you're using OS X, this is another good reason to use Omniweb with Radio. Omniweb supports spell-checking on all text-boxes, including progressive "underline the words I don't recognise" checks.