Not perfect, but pretty cool.
First of all, it takes place in a brand new region that is nowhere near the regions of the previous games. That's a pretty interesting approach. Unfortunately this makes many of the older Pokemon inaccessible. Fortunately you can transfer your Pokemon from the Gen IV games. Unfortunately they can't have any HM moves or be holding any items. Which is kind of lame to tell you the truth. That means I can't transfer a Pikachu holding a Light Ball to my game.
The Unova region itself is awesome. Not only does it have night and day but it also has seasons. However unlike with night and day, the seasons are not in real time. They change every month; for example Spring in January, Summer in February, Fall in March, and Winter in April. There is also a bridge that actually features cars. Also Castelia City has a unique perspective never seen before in a Pokemon game. At least not in the handheld games. Sadly, the Pokemon don't follow you around like they did in HeartGold/SoulSilver. I really liked that feature and was kind of disappointed that it wasn't there in Black/White.
My favorite new feature has to be the fact that TMs are now reusable. I no longer have to choose which Pokemon to teach a TM move to. I used to hesitate to use TM moves because I was worried I would use the TM on one Pokemon only to wish I'd saved it for a different one. Of course most of the TM moves are nothing special and you still have to use strategy while teaching HM moves.
The biggest letdown was the absence of rematches which have been a staple of Pokemon games ever since Generation II. Also I wish that berries were more readily available outside of Global Link but at least the berries are there, unlike the rematches.
I'm not too crazy about the designs of some of the new Pokemon. However, to be honest, there were designs I didn't particularly like in previous generations as well. So I have no real complaint there. There are also more than a few cool Pokemon designs as well.
Bottom Line: Pokemon Black/White is a decent installment of the series. It has some new features and implements several improvements. However there are also things that are left to be desired. I hope that at the very least, rematches return in Black/White 2 which seems to be the next installment.