I've had one about 3 or 4 years and like it very much. I shoot it quite a bit because I take it to the range when I am shooting other "fancier" guns and testing loads etc. I shoot the Marlin while waiting for other barrels to cool etc. It has close to 2000 rds through it now. No problems at all.
It likes 240 grn Hornady XTP's--17.0 grns of 2400 for plinking and 21.0 grns for hunting. And that bullet is a good deer killer in that rifle. The 265 grn. Hornady FP shoots well too.
I have no idea if my barrel is "oversized," but it will put 3 shots of the hunting load under an inch at 50 all day and I have had three shot clover leafs several times.
It shoots cast pretty well--2 to 3" at 50--with 7 to 8 grns of Unique, but I have not worked with cast bullets much yet.
I have a 2.5 Leupold on mine right now, but I have shot with open sights, peep sights and a red dot Aimpoint and they all worked well with it.