After reading the Android blog entry about releasing 1.5 for the dev phone I could not resist installing it. By following the instructions on the HTC site all went well. I used the ADB method (image recovery) No problems whatsoever!
To get a connection with the phone network operator I had to reboot a third time (1st time: radio firmware, 2nd time OS 1.5).
My first impression of the GUI is that it is a bit sleeker, but sometimes feels slower.
Video recording and automatic screen rotation both work well. The touch keyboard and voice command options are welcome new features.