I was happy to see myself in the top 200 when I checked it out yesterday. I finally got to the top spot on my realm which is pretty sweet too. During my time on this site I've been slowly climbing that ladder to get to the second spot multiple times only to see someone new appear with a bunch of CE pets and beat me out. I put in a lot of work farming for wild rares and grinding out battle-stones in preparation for this change, and it feels like it paid off.
It's nice to see such a varied number of total pets on the leaderboards now. It used to be that the top spots were all nearly identical collections with just a few region-specific pets being the difference. I'm sure it's a little disheartening for people that have always been on top, but it seems to me that having all of those rare and/or expensive pets can still give you quite an edge. It's just that now there's actual work to be done to be able to capitalize on it.
Personally, pet battles have been a huge addition to the game for me. I used to be a somewhat hard core raider back in Wrath, following my progress and gearscore against my realm on sites that tracked such things. All during Cataclysm, after my guild fell apart, I still played, but had no real direction and struggled with finding things to do. It's nice to have something I can be competitive about again, even if it means more to me than it does to most other players.