Plenty of benefits; improved support for REST is a major one, but there are tons of little fixes that make life much easier. The link in chaostheory's comment is a good overview, or (if you feel like spending $9 more) you can buy Ryan Daigle's Rails 2 PDF at http://peepcode.com/products/rails2-pdf - Daigle runs a well-respected blog that keeps track of the newest developments in edge, so was able to pick out the most important things to write about.