Build 5231 of Longhorn is one of the last betas to come out, and one of the last to feature "Luna", the UI in Windows XP.
The setup process now looks very much the same as Vista, but the background and color scheme is different. A few of the steps are also slightly different (such as partition creation).
The splash screen is completely unchanged.
As with the previous build, it seems to be necessary to install additional drivers. Build 5231 comes bundled with a "supplemental driver" installer that apparently downloads and installs XP drivers that Longhorn doesn't support directly.
This build changes the glass-like appearance again, such that it looks more like embedded Windows than anything else. However, much of the rest remains the same.
The start menu now works similar to the one in the final release of Vista.