Usually not the most accurate. Due to the bad lockup of a lever.
I've never noticed any problems with any I've had. Most of the Marlins I've shot have surprised people with how accurate they can be.
As far as how good they are they have sold over a millon of them so that should tell you something. I've shot deer out to 200 yards with mine with no problems. With the new Hornady shells they can shoot well past 200 yards.