2-21/2 inches. I have 3 inch heels, but those are for going out purposes, and that's that. I've been getting more used to higher heels lately, but it scares me that I'll get so used to them that I'll wear them too often and thus ruin my feet. I have a tendency to bunions and I really hate bunions: not because they look bad (though I honestly think they do) but because they look so painful :S I'll try my best not to get them, my spine will be grateful to me about that as well.
I suppose it's different for women who drive to work evey day instead of commuting on public transport. You hardly ever see women in really high heels here in Barcelona, although I've heard it's different in some other Spanish places