I prefer a handwritten address on things, but I like using printed labels or envelopes with our return address. This year I wrote both the address and the return address on all our Christmas cards, but that's because I didn't feel like digging through boxes to find my labels and I spend a few evenings on the cards anyway so a little extra work was fine with me.
I'll agree with the others though, I don't care much for the preprinted cards. A mailing label doesn't bother me too much, but combined with a preprinted card...they just seem too impersonal. I love including a few notes in every card to wish people well and I'd almost rather not receive anything in return than get an automated response. Those picture cards of kids or pets are cute and I enjoy them, but please include a little sticky note or something on the back of the card!