The only thing I hate is how sometimes a document compiles perfectly fine on one machine only to utterly fail on another. On the two machines were I had this happen I have Texlive installed so that I wouldn't have to look up missing packages. Maybe this is a version mismatch error? I have no clue.

Also I had an old document I wanted to compile which used a '\begin{justifying}' tag. I can't get that tag to work anymore and had to replace it with just '\justifying'