As always, please give the latest C5 release a spin. Download it from SourceForge here.
Click here for release notes. We're pretty proud of this one. Due to some of the improvements (caching, customizable themes, marketplace integration, lots of bug fixes) we're anticipating a little bit of bugginess on this, which is why we're not quite ready to call this 5.2 stable. We'd really love everybody's help getting it rock solid, so test it out if you can.