Yes, bash has it's shortcomings, but it's good to know it nevertheless, because it's used by many people.
That's changing though. For example, /bin/sh no longer points to bash on Ubuntu; it points to dash* which is basically FreeBSD's sh** which in turn is a subset of ksh. So from a scripting perspective you should learn POSIX sh and steer clear of "bash tutorials" (Wicked Cool Shell Scripts is a pretty good book). If you want to use more advanced enhancements (non-portable) to the sh language or get a better interactive experience just go to the source: ksh. bash is just a bigger subset of ksh.