I bought a 336 from Bass Pro around 3 years ago, and haven't had a complaint.
Works just fine and is pretty damn accurate as well.
It is the cheap model and fit and finish is what I expected. No huge gaps, or any noticeable blemishes, but definitely not the same finish and blueing as the older models. Not polished up like some of the old examples, but in todays market for $450 brand new WTF do people expect.
I should also say that I just recently(last dec) bought a Marlin XS7 in .243, and the same can be said about it as the 336. A great gun at a great price, and nothing to really complain about. This one was only $380 so again I got my money's worth and then some.
And I almost forgot the little Marlin model 915y I bought this year. It is the single shot youth 22 I bought to throw on the quad for grouse on the trails up at the cottage. I paid $200 shipped to my door and it looks and works just fine. The little plastic block that sits in the action where the mag well would normally be seems pretty cheap and kinda loosely fitted but it hasn't been an issue yet.
So I think I have a little experience with Marlins in the last few years, and I really can't complain. The guns I have bought were all cheap, and they all have performed as expected, and better. No major fit and finish issues for me.
The way I see it is if you want a showpiece you have to pay for it. I don't think this is what you get when you buy a Marlin, and if that is what your expecting you might be disappointed.
Obviously function issues are another story but I haven't had that issue.