FWIW... I checked my framerates using both an older build of MC14 and the latest one, with HQ Drawing enabled (set to High in the current build). Both versions stay pegged at right around the 60fps target on my machine (around 150 fps capable). I somewhat expected this result.
However, the new build is FAR more responsive when using my remote keypresses via Girder than the older build (was 14.0.37). Still not quite as responsive as when I have it set off manually, but still much better (though not quite "usable" I'd say).
Still, one example of the behavior I'm seeing... When I'm in Theater View and I have a view open with a long list of files or categories showing (such as a Movies view showing a list of all of the movies in my Library), using Lineup View Style.
With HQ Drawing Off (set to Low): I can immediately hold the up and down arrow keys down on my remote and it will "fast scroll" through the list. When I release the key, it will stop scolling. EDIT: If I hold up/down for a long time, or repeat the activity a lot, I still actually see the slowdown described below, but it is much more mild and takes a lot more "scrolling" to occur.
With HQ Drawing On (set to High): If I immediately hold down the up or down arrow key, it will slowly scroll through the list one item at a time, as though I were manually tapping the up/down key one "press" at a time as it goes down or up through the list. When I release the arrow key, it will keep going for a long, long time until it has "caught up" to all of the keyboard repeats it has been sent. The longer I leave a particular view open, the more it "calms down" and starts working normally. After 10-30 seconds, I can get a 4-5 item "fast scroll" before it slows down and again starts going one at a time. After 45-75 seconds, it starts working mostly "normally" (fast scrolling works and keypresses are responsive), with only an occasional hiccup. However, if I drill up or down through the view, or change to a different View, then I go back to square one.
Again, this only applies to using my remote control via Girder. If I use a regular keyboard, it seems to work fluidly either way (though I think I can detect an ever-so-slight lag even with the keyboard, though this could be psychosomatic).
I haven't attempted to address this with various settings tweaked individually, but I did try disabling VSync initially and it didn't seem to help.
BTW... When you are testing this yourselves (Matt et all) do you have Adaptive AA enabled (and set to Quality) in your Video Card drivers, or are you just running them stock?