I'm partial to this road because, as censor46 says, it is a great shortcut to avoid Harrisburg, but also because it goes through my town. And then there's the ferry!
PA 34 begins at US /15 on the west side of the Susquehanna just south of Liverpool. If you happen to be on the east side of the Susquehanna, catch the historic Millersburg Ferry (
http://www.millersburg.com/attractions/ferry.html) and cross to the landing opposite the start of PA 34, then proceed south through three courthouse squares (New Bloomfield - Perry County, Carlisle - Cumberland County, and Gettysburg - Adams County). Note the Union Civil War monuments in each, especially New Bloomfield. Scenery takes you through curves in the Appalachians, then across the broad Cumberland Valley, and then into the orchards of upper Adams County before you enter Gettysburg and the battlefield.
PA 34 is for cruising, and except for a few curves, is not a sportbike road such as the next road west - PA 74.
Fred
P.S. The ferry is seasonal. Check dates, times and flood stages before making any assumptions.