It's a mixed bag. While it's probably the weakest season since the second (not counting Fast Forward), and there's a lot of awkward bits (most of the new characters could have used more development), it still has a lot cool stuff in it--moreso than other seasons.
A spoiler-free rundown:
The first act--The Ninja Tribunal to More Worlds Than One are all decent set-up episodes, and develops the new characters and status quo.
Episode 5.5, Beginning of the End, tries to be dramatic, doesn't really succeed, and is generally dissapointing--the potential is there, but it really could have been lots better.
Episode 5.7 is Membership Drive, which you've probably already seen.
The next couple of episodes are a two-parter called New World Order, and is the definite high point of the season, and maybe the series.
Fathers and Sons is decent--there's a plot element that's somewhat surprising, given the show's audience, but other than that, there's nothing special about it.
Past Present is filler, for the most part.
Finally, Enter the Dragons, is the big finale, and while there's a lot of good moments, the story as a whole is somewhat dissapointing.
All in all, it's probably better than Fast Forward, although I liked that season more than this one--this one reminds me too much of the worst aspects of Naruto for my tastes.