I've only played XD, but, personally, I loved it. I greatly enjoyed the double battles that dominated the game, and the Shadow Pokemon was a very nice capture system. I didn't have to farm each area to get all the Pokemon there, you just acquire them all as you go along, and, should you miss one, you can recapture it later.

The only real downside is that a lack of breeding and the fixed captures means that getting high IV Pokemon is nearly impossible, and battling only trainers makes EV training hard (fortunately, there is a repeatable trainer who has only Speed EVs, and one who has only Special Attack EVs, so it's not impossible).