MS is reporting nearly 80% success with all machines upgraded to SP2, with most of the rest being considered "failed" due to legacy hardware/software issues, incorrect installation (RTFM), and corrupt downloads.
Doesn't sound like much of a failure to me.
Also, as with every other SP and new release, legacy hardware and software get dropped. This is part of the advancement of the OS as new technologies and the average market change and are implemented.
If you've got some rare peice of hardware, a legacy hardware or software item, you didn't read the documentation, or you downloaded from a 3rd-party site, that's just tough beans. The number of people suffering from fatal problems not covered in the above, are few and far between. There's more smoke than there is fire.