I concur, yesterday evening (during and after champions league games) a lot of channels had ECM round-trip time of > 800 ms, causing a lot of freeze, etc.. it is usually less than 200 ms for me (server ping is around 40ms).
I've also noticed for the past few weeks that not all Sky Movies HD are working at the same time: usually one channel is not descrambling, but it's not always the same one.