If anyone has done this by car, about how many hours and road conditions?

Many thanks!!!

Based on my having done the main segments of that trip -- but not all at once -- I'd estimate driving time at 3-4 hours.

Road conditions are good, but as you leave Attiki (Athens region) and rise into the hills & mountains toward Delphi, the road becomes 2 lane.

I think the best maps for planning a driving trip are the Greek 'Road Editions' series. They are often available at kiosks, and can also be mail-ordered. See:
http://www.road.gr/road_en/index/default.htm

Also wanted to add, that if you stop for viewing scenic vistas along the way, it'd be best to add at least another hour.

Thanks!!!
good resource; also learned about viamichelin.com

Yes, Via Michelin is good for estimating preliminary driving times ... but I often add an extra 50% to their calculated driving times

The "clockwise" journey Via Michelin suggests (west to Patras bridge, then east to Delphi) is scenic, especially the eastward drive along the north shore of the Corinth Gulf ... but with the various stops you'll be tempted to make, this will likely be a 6 hr trip.

Within 45 minute drive of Delphi is the small, pretty coastal resort town of Galaxidi ... Time permitting, I think Galaxidi is worth a detour and a stop for drinks or a snack.