I've always been a big fan of the zsh shell. Lately I switched back to it at home after a long time using bash. Everything was going wonderfully, until I decided to get my character sets organised and switch to a unicode locale.
The zsh version in Debian stable is 4.2.5, which has extremely poor unicode support. Typing characters such as £ at the prompt confuses things, and lets you do corrupted things like backspacing over the prompt display. After some investigation, I found the problem was zsh - in the 4.2 series, unicode support is very limited, and you need to switch to the 4.3 development series for things to start working sanely.
First I tried to download the source deb from Debian testing and rebuild it on stable - this failed, so I went for letting someone else do it for me, and am now happily using the 4.3.2 zsh build from backports.org. And now I can type £ and have it be displayed properly and treated properly as a single character. In theory this is a development release, so there may be other problems, but from what I can tell zsh is very stable even in the development series.