You can expect performance in the range of a P4 3.0-3.2 GHz depending on what you're doing and who you ask. No worries there for WoW.
Screen is sufficient. HP doesn't have a dead pixel problem as much as other builders.
Only potential problem is the 200M IGP, don't expect to run it with all the bells and whistles maxed. If you are willing to spend more money, you can look at the dv4000 or v4000t with a 128 mb x700 and centrino. But personally, I think the main bottleneck for WoW is RAM. You might want to look at more RAM later.