I finally decided to roll out SoftGrid on my home network and it seemed to go very well at first. 4.1 SP1 on the server, 4.2 clients. Some clients are XP SP2 and others are Vista (Business, and Ultimate editions).
The weirdness is best described as follows:
Windows XP SP2 clients - Slowness overall. The sftddc service seems to eat quite a bit of memory and CPU cycles, regardless of whether the AVS server is available over the network or not. As soon as I uninstalled the SoftGrid client, the performance levels seemed to improve overall.
Windows Vista Business clients - Not much (adverse) impact at all, however, that machine is running on 4GB of RAM (32-bit install equates to 3.x GB)
Windows Vista Ultimate clients - Performance appears fine, but the oddity here was with desktop and start menu icons. About 50% of them got wacked and replaced with broken icon image links. Most were fine when I visited each one to change the icon for the shortcut, however, some still refused to display correctly. This didn't happen immediately either. It seemed to start about 12 hours after the SoftGrid client was installed. After I uninstalled it, everything went back to working and displaying properly. Weird.
Don't get me wrong, I'm really optimistic about SoftGrid as a whole. It is a very cool and exciting technology. I'm hoping my experiences are something that will be addressed by the 4.5 upgrade. I'm going to attempt that in the next week if time permits. I do know that Microsoft acquired Softricity at a time when they were still getting their mojo together. A lot of features in 4.1 and 4.2 are simply unfinished or half-baked. Documentation is also sorely lacking. However, I also know that Microsoft is applying a serious effort behind addressing all of those issues. Even 4.5 is admittedly an "in progress" effort. The version that follows behind that, which will also be known (at this point anyway) as "Microsoft Application Virtualization", will be significantly improved and will play nicely with System Center and Active Directory.