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.
* http://manpages.ubuntu.com/manpages/lucid/en/man1/dash.1.html
** http://www.freebsd.org/cgi/man.cgi?query=sh&apropos=0&sektion=0&manpath=FreeBSD+8.1-RELEASE&format=html