Full changelog is here; highlights include
new-style active tags - docs OpenACS-like (Tiles-ish, for you JSP people) parent/child templating system - roughly the same speed as include.spyce, so using one parent template has about 1/2 the overhead as the old standard two-includes-for-header-and-footer. - docs Active Handlers reusable components without the leaky abstraction of ASP.NET et al. - docs
The only major change since the prerelease was announced on this blog is that the class chunk token was changed from [[\\ to [[!. At least that's the only one I remember after spending the last 5 days wrestling with sourceforge's cgi-bin.