It totally looks like a beta more than anything else. I can understand that it's a secondary thing... yet Blizzard usually don't release anything untill it's done, well Pet Battle System is definitely not done.
Leave apart the fact that it's pretty much RNG, as it kinda depends on the combos you fight;
The level of pets it matches you with is not exactly correct, you can easily find 2 really low level pets or two hugh level pets.
Pet store pets are overpowered... the best example is the ridiculous Pandaren Monk, able to 1 shot any pet in 2 turns: 1 buff up (100% crit) 2 attack = one shot. In my opinion, if it doesn't change it will only show how the pet battle system was an attempt to make players buy pets.
There are also many bugs and meaningless things. For example, planting mines that should explose when your enemy switches a pet.. I've seen many of those mines explode at random times.. sometimes when your oponent switches a pet, otehr times when he switches for second time and that if you are lucky, 40% of the times mines won't really explode at all.
Dodge... that's really lame, there shouldn't be any dodge/miss. You already depend on the set up you fight, which you can try to face as good as you can with your pets and spells... but you can easily enter a chain of 3 attacks dodged.. .that's plain wrong.
How's our experience so far with the system? I believe that it could be quite fun if they really sovle the issues.