Hi Shawn,
This is the route I took.
http://www.google.com/maps?f=d&hl=e...7476&sspn=0.724696,1.277161&ie=UTF8&z=10&om=1
Generally speaking, I found the conditions of the roads to be excellent.... far surpassing what we have to deal with here in Mass. Some parts of the drive were excellent, some were boring.
Plymouth to Wentworth - Pretty boring, but necessary because the drive from Wentworth to Lincoln is really worth it. Lots of twisties and through a park with limited traffic. A definite highlight as far as the driving experience on this route, although there aren't any views (which may be a good thing).
Lincoln to Conway via Kangamagus - A pretty drive. Moderately twisty with great vistas and I'd definitely recommend it as being worth the time.
Conway to Twin Mt. - Conway is pretty commercial and in my opinion would be better to avoid it, if possible. Bear Notch Road in Carroll is an intruiging possibility but it would definitely need to be scouted out as I have no idea what condition the road is in and it could be really rough. Crawford Notch is really nice, easy driving with some views and has a great place to stop off for lunch or a break. Just south of the Mt. Washington Hotel is a new lodge that was built by the Appalachian Mountain Club that I think would be a great stop.
Twin Mt. to Bath - A dud, both scenery and driving wise. I'd definitely skip it in favor of going through Franconia Notch, which is is very, very beautiful. Best route is coming thru Franconia from the South to the North.
If I were to do this route again, this would be the route I would take. Bear Notch Road would be an option, depending upon road condition and drivability.
http://maps.google.com/maps?f=d&hl=....007632,-71.575928&spn=0.885991,1.716614&z=10