I've now been contracting as a developer for as long as I was a permanent employee and I've learnt more as a contractor. Sometimes it's been a bit of luck with a job but the rest is mostly from only having to do the job you're in for - so no reviews, company meetings and the rest, plus I can pick and choose (and afford) to go to more workshops and conferences.
It can be easier to be complacent as a perm employee but less so as a contractor.