The pictures below show my enjoyable experience walking a portion of the Rockingham Recreational Trail on November 2, 2012, about a one-hour, round-trip walk from Locksley Lane. I prefer walking away from road traffic, so the abandoned railroad bed is perfect for me.
The entire trail is about 27 miles, extending from Lake Massabesic in Manchester to Great Bay near Portsmouth. I walked from Prescott Road to within sight of the Depot Road. The trail is firm, with a few nuisance places with branches or wet spots. You can certainly walk at a brisk pace or ride a cross country bicycle with ease. The trail does have places close to route 101 which are noisy. The sections where you can see the Lamprey River are the most interesting. Give the trail a trial, and I think you will like it!
Old railroad bridge over the Lamprey River
Map from http://www.traillink.com/trail/rockingham-recreational-trail.aspx