Glass .. Glass, baby! :-)
Well, I did it! Today, I installed Windows Vista on my Tecra M5 and got everything including Aero Glass working just fine. I managed to get a Windows Experience Index of 3.0 (see picture below), which I understand is pretty good.
I think that I’ll use this as my primary machine from now on since I run the MOSS demos on this box anyway (still need to get VPC or Virtual Server working on Vista). I’ll use the M400 as my backup machine for newer builds of Vista and Office 2007.