I personally haven't noticed any worsening of PQ over the past 2 years, but, if there is any PQ issue stemming from bandwidth, it would most likely have to do with the expansion of HD services. Each HD channel takes up the bandwidth of 4 to 6 SD channels. As they try to compete with the other providers for HD content, they must be getting very creative making their aging satellites carry this additional bandwidth. I noticed that the PPV offerings are very thin compared to Bell - ever try to use 6 PPV credits in 6 months without watching XXX? I think it's to save bandwidth for HD.
The digital compression leaves artifacts and even without a bandwidth crisis, the PQ on a SD channel is better on C-Band (Analog) than any DTH sat provider or digital cable provider.