Much of the criticism aimed at hip-hop and rap are the offensive and viloent tone of the lyrics. Seems like I've been binging on Outkast albums lately (the latest one plus "Stankonia" and "Southernplayalisticadillacmuzik"), and I'm continually impressed by the complexity and topics of their lyrics.
Outkast certainly won't win any awards from the 'moral majority', but their lyrics rise above the standard verse-chorus-verse, and songs like "Get Up, Get Out" (from "Souternplaya..."), are simply amazing to listen to.