Havent got a bike yet, but I'll share my research with you -
A lot of dealers (about half of them) I've talked to have tried to steer me away from a drop-bar bike when I tell them I want to put a child seat on it. They say it's too unstable. Others say it will work fine, you just need to practice a bit.
I've exchanged emails with some bloggers in the US who have done it and say it's no problem at all (particularly with the iBert Safe-T front seat and the Co-Pilot Taxi/Limo rear seats) although everyone seems to agree that it's more comfortable and convenient with a flat bar bike.
Given some of the countless pathetic and avoidable low speed crashes I frequently witnessed when I lived near the Danshui bike path, I think a lot of people here try to take up biking in adulthood and have no idea what they are doing, thus the dealers' general trepidation when recommending family bikes here (get a small frame, dont get a racing bike, get an ATB etc.)
Anyway, if you do go with a road bike, I'd recommend a seat that sits as low in the back as possible. And most front seats dont work at all - that iBert one is the only one I've seen that works on (some) road bikes. I'm probably going to get the child seat I want first and then pick a bike based on that (although I'm feeling pretty confident that I can use a cyclocross bike for whatever I want).
Hope that helps! I'll let you know what I end up going with (if I get my bike before you do)