A humorous summary of what a WoC plays like goes something like this.
1) Buy WoC
2) Deploy in a straight line
3) March everything straight forward while blasting with magic
4) Charge or be charged
5) Kill everything in combat
6) Continue into opponents deployment zone
7) Count victory points
In all seriousness, my girlfriend is just starting a WoC army and it's no surprise that they are undisputed masters of close combat. Thier most basic infantry slices through just about anything with ease. They have an incredible selection of magic items, marks and gifts available for customization (thank the chaos gods?) and formidable casters that can go toe to toe with the best the game has to offer (from what I've seen/read). Their biggest drawback, that most people easily identify immediately upon reading through the book is their lack of any significant shooting. Even when compared to Lizardmen (whom only really have skinks, terradons and howdah wepaons) they seem weak. The only elements that really offer anything in the shooting phase are marauder horsemen and of course, the ever interesting hellcannon.
While their powerful units are very elite, WoC has access to cheap troops as well. A unit of 10 foot marauders costs a scant 40 points with no equipment and can effectively redirect charges or simply get in the way of enemy troops. Another potential problem the army faces is its speed. Comparing to LM once again, WoC lacks a significant amount of troops that are mobile. The greater portion of troops that are used seem to be standard MV4 infantry. A few people in the gaming group in which I play think that the army can be difficult to play (which I think my girlfriend is realizing). The primary reason being because of the focus on the movement phase, where in order to be competitive you have to be an expert at unit placement or you find yourself out manuevered, flanked and broken quickly.
This is just my overall impression of the army, but I have also been interested in playing it.
*edit* Spelling, punctuation