Yes. Yes they are! The Mosin-Nagant is inexpensive, yet rugged, reliable, and capable of surprising accuracy. It can also be fed pretty economically with surplus ammo (which is still very available, I believe).
Several companies and individuals make scope mounts for them- I recently found www.mojosights.com, which makes peep sights for a variety of surplus rifles. I intend to mount a set of these on my Mosin, which should give me a rifle capable of hitting a man-sized target out to 400 yards (at least).
Come to an appleseed. I run a Mosin Shoot at my club. 200, 300 and 600 yds. Prone, slowfire with nothing but the sling for support. Stock rifle, surplus ammo and the blue pistol targets. Appleseed grads always win. http://www.appleseedusa.org