Any setting for "GUI Scale" aside from "Auto" seems put a lot of extra stress on my computer's graphics card. This is pretty annoying for me in particular, as my PC in particular tends to block all hardware input when the level of stress achieved by opening certain GUI's (notably chests) on the other settings is reached.
It should be noted that, while the visual output is pure black when my computer blocks hardware, the games ambiance music can still be heard, which implies that Minecraft's software continues to run. I can confirm that it is a problem with the game, however, as the particular issue my computer has rarely occurs without an impetus from the software, and I can frequently replicate the results on my machine with nothing running but Minecraft.
This is probably not a highly visible issue for people with better computers than mine, but if it's possible to increase the efficiency (or at least tell me why it does that) it would be great for everyone.
Tested in Single-player with pretty much all combinations of graphics settings. No GUI's except the chest seem to cause computer crashes on any game modes, settings, or world types. Chests crash on settings aside from Auto on all world types and outside settings, but no crash occurred for any chest, fullness level, or scale setting on Creative mode. Even without crashes, however, changing the setting from Auto seems to have caused a noticeable amount of lag.