There is a pretty good amount of bike paths in my area that are flat and scenic but most importantly, are away from the traffic (that there is also a good amount of). A road bike is so overkill for that type of ride, even if you can do 30 miles of bike path if you want to. What, you need 20 gears and a 17 pound, carbon framed wunder-bike to do that? Pffhaaa!
But a mtn bike set up for dirt, even a 29er, is not really great either, what with knobbies and flat bars. So, I have plans for the Karate Monkey. The versatile Monkey, the Swiss Army knife of cheap 29er frames. I need to get a rigid fork and then I will build it up with the wheels that are now on the SS Jabberwocky, soon to be spinning around on new hoops. That will mean lacing up a new rear DT Swiss 7.1 TK rim (crash damage that makes a rim brake an issue), but then I will choose a singlespeed gear that works as a compromise on flat trails and moderate hills, add some kind of an alt handlebar and cheap Avid rim brakes, use some shorter cranks for the big spin, likely an old XT square taper with some ancient BB...tadahhhh! Urban rage machine and bike path monster/curb hopper/spin master/attack cruiser.
Hah. I can hardly wait.