The expansion to the best poor man's MMORPG in graphics, gameplay, features. This expansion is much better than AION!
I agree with other reviewers that the new mini-games (Asuran Polymock and Norn Fighting Tournament) are lame, the Hall of Monuments is not nearly as cool as it could be (although it has improved significantly since release), and some of the dungeons are rugged (SOMETIMES on par with the elite dungeons in the three campaigns, but often not).
However, it is great at doing what GW does best: fun fantasy/adventure role-playing in a rich and vibrant world. If you liked the others, you'll like this (if not, then no). What's nice and new is that the story branches into the Jurassic/meso-American Asuran line, the forested Char line, and the snowy Norn line. This way, you always have something fun to go do, even if you get stuck or bored with the scenery or whatever.
Despite all the complaints about reskinned armor... the new stuff generally looks really good and gives you a way to reward characters who have fought long and hard.
The new skills add a great dimension to gameplay, even in the other campaigns. The heroes are super-fun. Most importantly, whether you like to explore, collect, achieve, or whatever, it broadens the horizons for your characters in both serious and light-hearted ways.
The 1up review on this site is totally unfair: There was a very satisfying amount of content for me just in the main story-arc... not including all the great side quests. I've done plenty of dungeons and most of the quests by myself or with one other person... and I'm not any uber-elite player. It is generally challenging on par with the later levels of the other campaigns, but I did not get nearly as stuck and frustrated as I did at the campaigns' missions. And to call the Norn "obviously Conan-inspired" as if all of GW isn't... "Thank you, Captain Obvious." GW is a great extender of the classic sword & sorcery genre... That's why it WORKS!
GWEN is the next step for people who are having fun playing GW, and it continues the legacy of awesome.