I live near the north end of the Blue Ridge Parkway (Milepost 0, Afton, Virginia). I sometimes bike portions of the first 40 miles and always find it GORGEOUS, but challenging. For me, Parkway rides are hands-down the toughest rides I do. I'm not a newbie, but I'm a slow, so-so strong rider, so your mileage may vary quite a bit!

I dug out this link to an elevation guide for the Parkway, in case it will help you when you're planning your trip:

http://www.blueridgeparkway.org/v.php?pg=15

There's a published guide to biking the Parkway but I haven't found it to be all that helpful. You're better off Googling for more first-hand reports like 7rider's.

Have fun planning!!