RE: 308 Marlin Express
Nope, don't own one. Wouldn't mind having one though.
To me this gun makes sense if you intend to scope it. If you don't scope it, you really won't benefit from the gun/ammo's higher performance, as your accuracy will be limited by open sights.
Personally,I don't like the look of a scope on a lever gun, so buying one of these is not a priority for me. I have an 1895SS in 45/70 with a peep that is awesome.