I hope in addition to the revamp that the NOW TV box resolves the stuttering playback issue.
From what I've read NOW TV - like Chromecast - only outputs at 60Hz. That might explain your stuttering if you're watching anything on iPlayer, which would be 25fps and doesn't go well into 60Hz. Some people just don't notice it, though.
It's on everything, from the Sky News and SSN HQ apps, to the NOW TV streams. Some of the live channels are more noticeable than others. GOLD for example has really bad stuttering ,poor lip sync and a grainy picture, while Sky1 is like watching a 544x576 Freeview picture with a low stream.
The LG set I own appears to have none of these issues as it also NTSC compatible.