Yes, I've seen many threads on other forums in which people are complaining bitterly about how much SL has messed up their Macs. Many are asking how to go about jumping back to 10.5 and others are holding out for 10.6.2
Printer problems, problems with Spaces... seem to be the most often mentioned issues, but there are many others.
Which is no different from any other change in cat names. How quickly we forget all the problems people reported with the move from Tiger to Leopard. I, for one, have pretty much nothing to report in the area of problems moving to Snow Leopard. It was probably the smoothest upgrade I have ever experienced in my time using Macs. Printers, scanners, modem, USB, external drives, no issues. Applications? Just waiting for Roxio to fix Toast 10 and CDSpinDoctor 6 which they say is RSN. Everything else works.