I don't notice any lag or drag on my LCD or my plasma. Really the only difference I notice is the reflectiveness of my plasma vs my LCD and the plasma has a slightly better picture in a dark room.
No to be fair most of the name brand LCDs including Sharp, Sony, and particularly Samsung have such high processing that to me renders their picture unwatchable, so I see the concern.
Now also to be fair most of the motion blur that I see on either set is actually in the source. I suspected this for a while and used my HTPCs to verify it. Between macroblocking and the motion blur captured it is hard for me to blame either display. For more on this see: When Is HDTV Going to Catch Up?