The isometric battles is everything.
I love the spells, the sounds, the moves.
I didn't particularly like the interface in the battles, it was a bit clunky and slow.
But the battles themselves were great, you had to really know your characters and their strengths, not to mention having a really good control of your available spells and when to use them, as just blasting flame lances about is too stupid. Even for someone with fairly good knowledge of 2nd edition DSA like me (they used 3rd edition for RoA), it still takes quite a bit of thinking.
No kidding about playing with the same makes it easier. Some fights are half-way impossible if you don't carry over your team.
As for my personal favourite: Probably Star Trail. I'm not sure why, I guess it's that it has the polish of part III and the expansiveness of part I. The differences are minute anyway, but II is my favourite
Many see the micromanagement as a pain... but talk about upping the realism factor.
The micromanagement was probably my least favourite part of the DSA games, but I never mind it much because the interface is so intuitive, and you can learn how to keep an eye out for your people without spending an infinity of time or clicking buttons a lot. It's not intrusive micromanagement, in other words, you just have to keep it in the back of your mind. Really well done, if you ask me, though it's still micromanagement.