The fish is great for transporting breachers, drones, and pathfinders. Transporting Strike teams seems to be a distant 4th option as they don't typically need the fish to get closer to their shooting target. As with most Tau units, we carry a bigger pricetag for having the FLY special rule since it enables us to disengage and still fire in most cases, the fish being no different.
Yes it is more than a rhino, but it carries more guys and it also comes with two drones so it carries a bonus two guys which can detach and give cover to the unit coming out of the transport for extra added durability to the unit.
It's a very good unit but I doubt you'll see more than two on the field as we likely won't take multiple units who need to crash the front lines as hard as breachers or drones. Luckily, Hammerheads share the same chassis so picking up several boxes won't leave you without good options to take.