The Eeveelutions are pretty disapointing, but I was never all that fond of Eevee to begin with, I thought most of his evolutions were pretty bland and ugly. There also seems to be far too many legendaries. What's going on with that pink/yellow thing and the Metagross look-a-like? These guys just seem unnecesary, not to mention *another* Regi.
However, I do really like the new Aipom, Magneton, Porygon, Murkrow, Misdrevous, etc. Most of the new evolutions of the old guys are really cool, I can't wait to see Magmar. I'm pretty happy with the game so far. It seemed like things were only getting worse and worse, I was extremely disapointed when R/S came out, not just because of the poor Pokemon designs, but the region itself was pretty horrible, but Diamond/Pearl seem to be a huge improvement. They just need to calm down with the Legendaries.
Oh, and also, there only seems to be 150 Pokemon in the game. Which means anyone who doesn't have the older GBA games is going to be missing out on a lot, including a lot of the new evolutions. Things like Electabuzz are not in the game at all, dispite him now evolving. Got to wonder if that's such a good idea.