We have released our second beta version of GeoServer 1.5.0. It contains many bug fixes and improvements. You can find the download here. Another useful feature it has is the ability to add coverages outside of your data directory.
Our next round of releases before the official 1.5.0 release are going to contain several larger changes that should clean up the UI and also introduce a suite of useful coverage tools, such as a Pyramid Builder and an Image Mosaic tool. This beta release will help us figure out what users want and need for the official release. So please try it out and give us lots of feedback either on our mailing list or on this blog.