I've got a 1953 Marlin 336RC, it shoots exactly where I aim it.
However, it also has a slightly canted barrel...Marlin engineering was 5-degrees off that day.
Luckily, its canted in the right direction, as it actually helps lock into my shoulder into the stock better!
Marlin's always made some sort of slight goof over the years, its inherent with inexpensive rifles...
but JM also built 'em like Tiger Tanks...tough as heck, last lever rifle you will ever need...
you'll be able to pass it down to yer grandkids
and they'll be able to shoot it!!
Unlike the "Presentation" Winchesters (safe queens)...or the Mossberg 464's that use questionable metal alloys...
I do prefer the pre-2005 Marlins, date code is the first two serial numbers minus 100.
If it is marked MM or MR, then a serial, it is a New Remlin. They have come a long way from the takeover...
I'd call the current ones as decent as the crossbolt safety models of the 90's...
However, Inspect a new Marlin as you would any new/used weapon.
Meaning...I'm a suspicious fella by nature. In God I trust, all others are suspects
Have a couple Snap Caps in .30-30 or .35-Rem, whichever caliber you plan to buy to check action function with.
Look for obvious and not-so-obvious faults. Start with the action, then the barrel, then the crown,
then work your way from crown to buttplate checking fit & finish.
Aim it, preferrably towards the ceiling

Check the barrel/sights for cant & warpage.
Newer Marlins...ok, just get the 336XLR if you are going to do it. Worth Every Penny.
They get extra care on the assembly line, as they are the Top Of The Line. It'll last several lifetimes.
Not to mention a really sweet deluxe recoil pad which makes a .30-30 feel like a .260
http://www.galleryofguns.com/genie/default.aspx?item=336xlr
Used JM barrel stamped ones...one month AFTER hunting season ends they start popping up in every gun & pawn shop...
just as quick as someone needs cash fast...some lose their pawns, to our benefit!
Many have deluxe pads, smoothed actions, some with big loop levers, ghost ring sights, etc...
all in what the previous owner wanted to do...
I look for old beaters...scratched-up stocks with smooth actions...usually the interior parts are spotless,
but the outside looks like crap, like a beat-up old farm truck, that's what you want
Lower cost if its rough, chances are it'll shoot like a dream.
The ones that have obviously not been internally cleaned in 5-6 years...those really go low.
Great news is, they can be cleaned up rather well...steel wool & gun oil

Again, built like a tank, so you just scrub the surface rust off and make it pretty again!!
I love stupid people who will literally shoot a gun until its too dirty to function properly...
then they say "Something's Wrong With it" and sell it cheap...and I buy it cheap...
clean the daylights out of it, refinish or replace the stock, new deluxe recoil pad, and have a great shooter
Hope that helps!! Good Luck!!