I have to add sth to this thread because some of us did some research on that topic on the PTR.
Semlar posted a test unit addon that had amazing results on the fps.
So who is into that stuff should read it.
Currently we are unsure why this
has such a positive effect on fps. If you comment out the hide function you see a massive decrease in fps. Even stuttering.
f:Hide() -- Try commenting this out and see what happens to your frame rate
f:SetPoint('CENTER', WorldFrame, 'BOTTOMLEFT', plate:GetCenter()) -- Position our frame relative to the nameplate
So doing SetPoint on a visible frame with many many objects (fontstrings, textures, frames) on it has major effect on fps. That same frame hidden before SetPoint and shown thereafter will not suffer any fps loss at all.
This applies to any project you have that has a movable object with hundreds of subobjects. If you drag that frame around...hide all subframes before you do so (if they affect your fps).
It is possible to fix nameplates. It should be even possible to create a new nameplate addon with the technique posted by semlar that will bring a performance boost when compared to the Blizzard ones.