I was doing internet support when ME was big, and I hated it. It was absolutely horrible, and it was all ME's fault. The restore feature didn't always help, and I can't even tell you how many times I had to rebuild the tcp/ip stack for dialup customers.
A lot of the problems with Vista was hardware and software compatability. People wanted their 10 year old hardware to work when manufacturers didn't make updated drivers. Software makers also drug their feet at updating their software for it. It was a bit of a resource hog, but most of those problems have been straightened out..