There's another thread on this here
http://www.pprune.org/forums/showthread.php?t=214604
I have an issue with "hold in position" (sounds like "holding position") but not with "line up and wait", except that I don't usually bother to include the "wait" (as per our MATS) unless the reason for any delay is not obvious. Eg: aircraft on runway; slower departure ahead etc is pretty obvious. Slower ahead in IMC less so.
We don't get too many Americans in this part of the world, but the few I've spoken with agree this phraseology is a disaster in the making.
"line up and wait" is not a conditional clearance, by the way, an example of that would be "Behind the xxx short final line up behind"