• Performance and stability improvements
You'll notice that the main features are Java-related. Specifically, the product is now at the Java EE 5 specification level which means that any web application that runs on GlassFish now also runs on Sun's Web Server 7.0 Update 1 (the implementation is actually taken straight from GlassFish). On the more technical side of things, you can use dependency injection in the web tier.
When released in early 2007, Web Server 7.0 enjoyed an excellent review and has been powering a whole new set of demanding web sites (including the one serving you this content). Any question, see the dedicated forum.