For those of you nearer Carrollton - the town is building their Greenbelt Trail which will be a 16 mile loop around the city. Around 7 miles are completed so far and it's open for riding. The section near the Lakeshore Park is the longest open section. Should be complete in 2-3 years. It's concrete with a center stripe and nice rest stops along the way.
I start most of my rides at the Rambo trailhead (mm22). From there going westbound the main features are the Pumpkinvine Creek RR trestle bridge, the Paulding Forest WMA and the Brushy Mtn Tunnel at mm31. That area is not crowded and you won't see the "scary looking" folks you'd encounter in the Cobb/Smyrna area.
The segment between Rockmart and Cedartown has some serious hills-It's like a roller coaster. The 1st 9 miles into Alabama are also very scenic.