Let me see, here is my interpretation of Season 5:
The season got off to a very rocky start when "Cheese A Go-Go" premiered, and to be very honest, it was a let-down than I actually expected, and it appears to be reverted back to Season 3 as its getting close to the season finale (which, honestly, happens to be my least favorite season).
Also, I am beginning to question the crew's choice of writer, specifically, Darrick Bachman. When he made his debut through Bloo's the Boss, I decided to reserve my opinion on him for a while. But after watching episodes like Emancipation Complication, Better Off Ed, The Little Pea and Ticket to Rod, I have to say that Bachman seems to lack insights of the characters, especially Bloo (one of my favorite characters). That, along with the humors and plot, didn't suit me well. For the sake of the season finale, I hope that he doesn't write the season finale.
Speaking of the writers, I really miss other notable ones such as Adam Pava, and I hope that sometimes in the future, he does an episode for Foster's again.
Finally there were some episode I enjoy, and some I didn't. But out of all the episodes shown so far this season, "Bride to Beat" happens to be my all-time favorite. The reason I choose this episode is mainly because of the relationships between Mac and Bloo, as well as their characters. In any case, it's clear that Bloo does care about his friendship with Mac, and Mac himself clearly enjoys Bloo's personality.
In general, Season 5 is on a so-so scale, but I hope Season 6 does a better job.