Personally, I think it could have and should have had a 6th season. I think they ended the series very well, doing away with Hugo Strange, but it seems like so much ground could have been covered in that season, instead of the Brave and the Bold practice run they had. You know, since most of the episodes were JLA team ups (which basically ammounted to "let's see who we can draw in The Batman style" for me). I think the show started out right, then they added Batgirl (which was a huge mistake, if you ask me...). I mean, Batgril pretty much came off as (if anyone has seen Jackie Chan Adventures) an older, Caucasian version of Jade (considering the same people worked on both shows, right down to the character desi9gners). I think season 4 was the turn around that made the show better (when they added Harley, etc.)
As for Brave and the Bold:
I actually kinda find it refreshing they DON'T have to make this Batman series dark to coincide with any of the films. I mean, Batman TAS had a lot of the Tim Burton films in it, and The Batman was clearly inspired by Batman Begins (considering Lucious Fox became a character... plus the first season reflected the movie's tone a bit more than the other seasons).
Personally, I'm loving the art style behind it. And I think it brings back sort of a Super Friends type feel, but with more sophisticated comic book backings. Plus, they finally gave Plasticman a cartoon show... considering the hillarious Plastic Man pilot went unsold.