Just beat this recently, and it was okay, but definitely wasn't as good as Colosseum.
>music is worse in most cases
>"improved graphics" means everyone looks like puppets
>despite having more shadow pokemon, most of them are shitmon and most of them don't appear until the end of the game
>citadark isle is a fourth of the entire game
>unlike colosseum which gave each admin a legendary beast, the admins now all have shitmons and all the legendary birds are crammed onto the final boss's team
>later trainers have 3+ shadow pokemon on their team (the final boss has SEVEN), making fighting them very tedious
>miror b sounds like a good idea in theory, but all you can really do is wait long amounts of time for him to show up and hope he doesn't show up while you're in the middle of something important
>poke spots miss the entire point of the game
>shadow lugia is disappointingly easy to purify
>orre as a whole feels more hospitable, which takes away what made it so unique
>removed some of the better areas from colosseum, like the under, and instead has shit locations like the ss libra and dr. pointless's house
>the lower starting levels make the early game much more boring
I will admit it makes purifying much less of a pain in the ass, and the added shadow moves make each Shadow Pokemon more unique. But overall, it feels like a step down.