These are my experiences with some ppcs. Only GG and OV have the ability to drive the really targeted traffic in volume to me. The others have conversions closer to my branding traffic of GG/OV, which is a lower conversion, but still an acceptible profit.
high traffic/great conversions: GG
high traffic/good conversions: OV, Sprinks
low traffic/good conversions: GoClick, ePilot, search123, FindWhat, LookSmart.
low traffic/average conversions: Brainfox, Lycos, 7search, Xuppa, and Searchfeed.
good traffic/average conversions: ah-ha.
high traffic/terrible conversions: kanoodle