Major players like Gohan and Piccolo are shells of their former selves. Although this is to be expected, Krillin, Yamcha, and Tenshinhan are no longer Z Fighters during the Boo Saga. Lastly, and I think this gets overlooked... I think Vegeta degressed in character development when he transformed into Majin Vegeta. This leaves Goku as the only one I like during the Saga. Also, kid Goten and kid Trunks are the worst Z Fighters in the series, although I still like Teen Goten and Teen Trunks over Professor Gohan at the End Of Z.
I like almost every major villain in the series... Piccolo Daimao, Piccolo Junior, Saiyan Saga and Freeza Saga Vegeta, Freeza, and Cell are all a colorful cast of major villains. Boo is the only one I dislike in all of his forms. Fat Boo, Evil Boo, Super Boo, and Kid Boo all have no character depth. I tolerate Bootenks and Boohan because I take them more seriously, but they're still poor man versions of Perfect Cell.
This doesn't get mentioned enough, but I feel like it's wasted potential as a closing Saga as well. During the 25th Budokai, I could feel the hype and tension of the atmosphere. The literal god king of the story (Kaioshin) and the literal demon king of the story (Dabura) both get shafted just in the Babidi's Ship portion of the Saga. The fact that Kaioshin did nothing about Freeza or even Cell but wants to ally up against the strongest and most dangerous entity in the universe (Boo) says a lot about the potential of the Boo Saga.
The plot holes in the series are more apparent in the Boo Saga than any other Saga as well. I could literally make a separate post elaborating on all of the plot holes in the 25th Budokai and Babidi's Ship alone. The early Boo Saga was once a heavily discussed topic on other older DBZ Forums back in the day. It's been discussed multiple times in the past and fans have eventually come to the conclusion of ignoring that portion of the story as a whole when it comes to ridiculous implications like Base Saiyans > Piccolo.
These are just my thoughts on the subject.