WarCraft: the RPG is fine in and of itself, but there are some balance issues if you transfer things wholecloth into another D&D setting.
Be warned that the races, feats and PrCs from the Warcraft RPG tend to be quite high-powered for D&D standards
Some people have suggested that WCRPG enforces an "Invisible +1 LA" for some, if not all of it's races. Consider that the Humans, who are the baseline of any setting have all the standard D&D benefits as well as a bonus to 3 charisma based skills and a +1 attack bonus against Orcs, and it gets kinda iffy as to whether the Tauren or High Elf's +1 LA is relative to the ECL 0 represented by the standard D&D Human, or this revised WCRPG Human. Mainly, I just don't think the LA's are consistant with the norms of standard D&D, and thus, are kinda iffy for inclusion in a standard game (But then again, I have the same problem with Oriental Adventures)
Now, keep in mind, that in April or Early May, we expect a 2nd edition, re-titled "World of WarCraft: The Roleplaying Game" to come out, and it will be using a racial levels system, much like Monte Cook's Arcana Unearthed/Evolved, which should remove Level Adjustments from the core playable races in favor of a 3-level Racial Class progression.
Aside from this gripe, however, most of the spells and feats are fine for import and export. If nothing else, Mysterious Purple Blast (from the Magic and Mayhem core book) makes a nice alternative to Magic Missile, which is good for at least a couple laughs. (One when you read it's descriptive text, another the first time your caster announces that he's using it)
Robert "WarCraft Fan" Ranting