If some of the channels on your provider are good, then it's unlikely that the service provider is at fault. If the provider were, then all the HD channels would look poor. HDNet, Discovery, provide good quality signals and you can tell.
See the following previous thread on the variations in HD:
As for SportsNet, please see the following thread which indicates some sort of issue they have with bringing in programming:
Ranting here and discussing the CRTC isn't really helpful if you don't understand what's really happening. For example, people ranting about Rogers compressing HD, when they are the one provider in Canada who does not compress HD channels!
"it's from the orginal broadcast feed and nothing to do with *C"
Typical BS that satisfies 73% of their customers.
To a significant degree, the CSR was correct, although there is some minor compression by *C, that's not what's causing the significant problems with channels like SN. So, although 27% of the people may not be satisfied with the "BS", it's not BS, it's true! Had the CSR said it has "little" instead of "nothing" to do with *C, the comment would have been completely accurate.
Another contributing factor to people believing that HD quality is going down is the fact that when they first got HD, it was new and looked great compared to what they had been seeing. After viewing HD for a while, it starts to become the norm and anything that's not excellent, then starts looking mediocre.