I still wonder how this series would have looked if the author kept the original premise of them being plants. I think making them cats definitely made the series more marketable, but it also makes it a bit more generic.
Either way, it's a great series. The start is a little slow but once the cast expands it makes the world feel very fleshed out and there aren't any characters I explicitly dislike.
I feel like Kei needs more screentime, though. He's one of the original three and it doesn't feel like he has had any development. He doesn't have any plot threads, and mostly only exists for jokes about him being feminine or being the tsukkomi to other characters.