The only annoying this I find in the otherwise indispensable GNU Screen is the fact that once you have launched screen (not resume) and have detached and logged off the first time, ssh-agent magic stops working in the screen sessions. Obviously this is because the next time you login, your ssh agent socket changes but the screen sessions still only have the location of the ssh-agent socket when you launched screen for the first time.
Texinfo manuals are used primarily by various GNU projects like Glibc, gcc, gdb, etc. Texinfo is an extremely powerful format for writing high quality professional documentation and can be easily converted to HTML, PDF, Docbook XML and various other formats. The language features tex macros which are quite easy to pick up, and much easier to hand write as compared to the new fangled XML formats. However, my pet grouse for a long time was that the PDFs, which look excellent on screen don’t seem to print too well on paper.