>>37148942One complaint I had is that the rental Pokemon were completely useless. In Stadium 1, the rental Pokemon usually had at least passable movesets, and they got better once you unlocked Round 2.
In Stadium 2, however, the rentals have stats lower than they should be, with all the evolved Pokemon having utterly useless movesets. The unevolved Pokemon have passable ones, but their stats are naturally much lower, rendering them a waste of time as well. In Round 2, I swear the rentals become even worse.
There's another issue where some of the AI trainers have illegal movesets. I recall one Blastoise that knew both Haze and Mirror Coat - these were egg moves at the time, but it wasn't possible to get both on the same Squirtle.