Usually the picture quality pretty good. However, I have just been watching Boardwalk Empire. Fairly static scenes are OK, if a bit soft. However, anything with fast motion seems to be a bit jerky and blurry - almost like an XVID encode when the bit rate has been set way too low.
I'm hoping they haven't dialled back the bitrate to use it for a different channel, but have no way of measuring this. It's not unwatchable - but it's getting close, and is pretty darn disconcerting.
jerky movement is usually a crap frame rate conversion. Thanks retarded DVB designers for not mandating flexible framerates so those of us in pal countries are stuck with this 50Hz crap.
Most of the time things are sped up to match, but sometimes for some inexplicable reason they framerate convert which usually gives 2-3 judders per second as it goes in and out of sync with the source, and I have seen frame blending which is an even more vile way of doing it in action on sky at times.
I recorded it and the following programme the next week. Boardwalk Empire again displayed all of these annoying symptoms while the Sopranos, which followed it, seemed fine. So it looks more like crappy NTSC->PAL conversion rather than a bandwidth/compression issue.
Personally, I would prefer if they just broadcast NTSC shows unaltered and had a STB that could seamlessly flick between the two output formats as required (as my DVD and Blu Ray players can) - most modern TVs can cope with NTSC signals just fine.