Even after playing a mage I still only used it during the first lessons at Winterhold. It takes too long to come up and then doesn't seem to stop much - would a bound shield or something have been better? Be interested to hear your point of view.

I find it quite handy, sure it breaks easily, and against continuos spells by high level enemies and dragon breaths is pretty useless, but against single-shot spells it's quite handy. And it blocks those annoying disarm shouts too.