I have to admit, rewatching series 7 of Red Dwarf has stirred up a lot of mixed feelings about this particular batch.
On the one hand, four years had passed since series six, allowing for advancements in CGI technology (meaning better special effects). Since Rob Grant had left the Grant Naylor team, his partner was left to collaborate with other writers, perhaps putting some familiar twists on old themes and to try a different tone. In fact, they brought back Kochanski, and Chloe Annett does a good job in playing posh spice in what was becoming, admittedly, a "sausage factory". The fact that they took several creative chances, including stylistic ones (such as single camera work and becoming more of a "dramedy") provides it with some really cool moments (including Duct Soup, Stoke Me A Clipper, and Beyond a Joke).
However, there isn't so much a "jumping the shark" moment as....well, approaching shark jumping territory. The new tone doesn't quite jell as often as it should, and much of it feels repetitive and obvious. It's also, at times, very tough to watch - one can understand why Rob Grant might have left, because series five seemed to be a high point, and series six had some more-of-the-same. (I would argue that Grant's leaving after Series 6 was like Monty Python's fourth season after John Cleese left - it was OK, but didn't quite match its earlier successes).
Your best bet to catch the funny bits? Look them up on YouTube. I'm not sure that this series is even worth renting. It's not bad, but it just has too much of a...well, smeggish flavor.