here's the official TV Club grading scale, so you know that B+ is not a problem.
A: I genuinely believe this is one of the ten or 15 best episodes the show has ever done, and I think even non-regular viewers of the show would at least appreciate it on some level.
A-: This is going to become a favorite episode of fans, but its virtues are perhaps less immediately apparent. Probably top 10 or 15 of the season.
B+: This is a very fun episode. Good and solid. If every episode was like this, the world would be a very good place.
B: This is a very fun episode with at least one significant flaw.
B-: This is a very fun episode with a handful of significant flaws.
C+: This could have been a fun episode, if not for the flaws.
C: A disappointing episode of this show. Hopefully, it will be better next week. (I use this score a lot for ambitious failures.)
C-: Also disappointing, but it's hard to see what the producers were thinking when making this one.
D+: Maybe one storyline works, but everything else is a mess.
D: Everything is a mess.
D-: Not only is everything a mess, but it's also dull.
F: I really think we should only use this when we believe we've encountered an episode so bad and so horrible that it is also sort of fun to watch in slack-jawed horror. Necessarily, that episode should be the worst or one of the absolute worst the show has ever produced.
And now you know!