There are people (myself included) who cannot remember how exactly to use tar, the Unix command. For me it always goes like this: "Is it 'tar -fzhf... ' or 'tar -vgsf...'? Ok, I'll google it again, just this one time, promise".
I don't think it used to? I remember needing to explicitly state tar -xjf for bz2 stuff. I do it now reflexively. If it's handled correctly by -xf, that's awesome!
Yes, it does, but only GNU tar. I was using NetBSD when I stumbled over the fact that it couldn't 'tar xvf' my foo.tar.gz.
OTOH, I always have to look up unzip, because I fear that there is some option that I forgot. Well, most of the time I use a GUI for Zip, since they often decompress all over the folder unlike tars which are mostly contained in one single folder.
I remember 3 tar incantations (to created a compressed archive, list, or uncompress one) that I treat pretty much as unchangeable commands. Probably should just alias them. Everything else I'll look up..