I liked 2.5 a lot but it suffered from the same seasonal collapse syndrome that all fishtank seems to go through, and towards the end I was just glad to get it over with as "The Cell" was just boring to watch, and they were getting too into "fishtank mode" where they'd just harass Jon, Tayleigh and Jimmy for content rather than write up interesting quests or events for the cast to do. I believe the cast did fantastic given the outdoors condition and weather they were subjected to and the NPC as well, even if some sort of illness passed through the ranks they did fantastic.
This was regarded as "beta testing" and training for the staff and I think it did a decent job at it. The only concerns I really have is with the HD cameras, Letty made a few comments that it changed how she reacted to stuff by making her self aware, and that different camera filming styles also influenced her, Tayleigh was a major change with her "Jim Face" stuff she was doing, when she was on CCTV and POV camera she was doing just fine and acted extremely normal like her S2 self, put a HD cam in her face and she'd pay too much mind to it. That top fish of two seasons had concerns and changes in their behavior to the HD cameras is something that should be carefully considered for Season 3, the goal is always to have the most natural reactions from the fish and if they start mugging for the camera its a problem.
The director camera was better but the audio cues like laugh tracks and waterhorn has to go, this influences opinion of fish and that should always be a viewer thing. Also the audio in "The Cell" that Tayleigh was in was Season 1 level bad with it being either impossible to hear or immediately peaking the microphones. They need sound dampening foam on the ceiling or its going to be a regression from Season 2 which had fantastic audio.