Massive changes. AND, if you have not been through these before, you will get frustrated until you get to the point that you know what you are doing somewhat ... use of spells and such, since it is all changed.
This, has to happen every so often. It happened on the first major, when the game went past 60, and then later when it went past 90. While tough to get adjusted to in the end, it's OK. It was so cluttered right now with so many spells doing the same as any other but just a different name, and color icon, that in the end, it makes sense.
The Pet Battles, since this site is about that, is probably going to lose a lot of folks now. Why? It will take forever to upgrade things and add up the Pet Charms, so you can get a rock to upgrade your pet to Rare, or to buy enough rocks to upgrade your own pets. I suppose this was designed intentionally so you would spend more time actually battling pets for upgrading, rather than using rocks to take your pets up. But the ability to get 750 pets and take them to RARE and then 25, is going to take way too long, and I think that many folks will get frustrated. I do think that the vendor prices for the Rare rocks should drop to 10, for example, and the upgrade rocks to 2 instead of 3. As of right now the inflation process is going to hurt the economy, and honestly, it can only happen if half the people that do pet battles stop over night and the folks at Blizz will go ... what happened ... and they might wake up. This feels like the concept of "gaming" that the old Everquest used to be famous for ... each upgrade was 1/1000th of an inch, and you were a dog if you asked for 2/1000th of an inch, and did not accept their game design for farming and camping from here to doomsday! (My bard never got the piece from the sisters in 2.5 years! Over 240 hours!)
All in all, it's still the same game, with just a lot of things combined into one, and I don't think that the "Talents" needed to be redone in its entirety, since some of them are the same, with a different name.But most programmers, never read/look at the previous code, because theirs is better and more perfect, right?
I say, stick around and continue some Pet Battles. IF, and this is a big IF, they increase the amount of XP that each pet gets on a fight, then it might not be so bad, but I can not see someone trying to get 100 to 150 different pets, to be able to make all your dailies and most Heroic fights feasible, and not being able to get there. I think that some fixes will be done, as is usual, in the first month of a new something or other. However, I, who have been here since almost the beginning (almost a month after its start), am getting a bit tired of the lack of over sight and historic effect that some of these changes have, which many folks do not like.
Some changes that I would like to see (in the pet Battles), would be to take some Pets off the stupid farming/camping process, like the Minfernal ... which is ridiculous, and it is not even a "major" pet to be used! I have yet to see one of them, and by the count of Pets and work into things, you know I have tried. It took me 3 months to get the Unborn Val'kyr, and I think that stuff like that ends up losing a lot of people. It doesn't have to become the vanilla stuff, but it doesn't have to be "sorbet" with a liquor, either! Baskin-Robbins is just fine!