The marker is quiet due to the low pressure (90psi) and no bolt. It is also a fast shooting marker with very few moving parts. Very dependable worst thing that happens is a slight leak that can be fixed with a new $2 O-ring from Sears! D-icer beads help to eliminate cold weather liquid CO2 problems that other markers have.
not much, a stationary barrel would have been nice
If you can't go wrong with this marker as your main gun or a back-up. They are not in production any more so if you are looking for one it will be used.