In my view it is entirely useless, I already know that the operation didn't work because it didn't select anything. And common sense tells me that I didn't point at the stuff I wanted selected accurately enough, so I try again. Who needs that popup there?

I use that key a lot, so that popup annoys me a lot. And i'm usually off only by a bit, so the first reaction is to just hit it again with the pointer closer to my target. But usually the damn popup is in the way and I have to get rid of it befor I can resume my work. It is just very annoying to me..

Is there a good reason to keep it?

Currently the term is applied for the Subdivison Surface Modifier and related activities, that's confusing for people migrating from other applications and it doesn't even make sense. "subsurf" makes me think rather of something like subsurface scattering than of subDIVISION.

What's worse people have started calling it "subsurfing" and stuff.. even in tutorials. Also there is tons of valueable knowledge about subdivision modeling principles from other applications on the web that new blenderheads might miss because they don't even know they are doing it. ;)

Personally I think it should be something along the lines of "SubDiv" if it has to be that short.

Weld all the selected UV-vertices together, that are within a specified range apart from eachother. ( like remove doubles )

This would be useful for some things that we have to do to save texture space in realtime application like setting up mirrored UVs.