I am by no means a great shooter, but I have shot with an M-14 at Camp Perry.
600 yards, no scope, no mount, no bi/tripod, no rest. A sling, ammo, an M-14 and you lying down.
It is easy if you have breathing control and trigger control. The standard PSO-1 scope is 4x magnification making it easier to see the target. As long as you are not a crappy shooter, and as long as you use decent ammo, you CAN hit a man sized target at 1,000 Meters. SVD, PSL, it does not matter. Most NDMs- 7.62x54R AND .308- shoot worse than the PSL for some reason. Shotgun News had an article on this. SVD style of operation but still piss poor accuracy.
If you want good long range ammo, and you do not mind corrosive, the Yugo 182gr. stuff is nice. If you hate corrosive, for close ranges you can use Olympic 180gr. FMJ and for longer ranges use Wolf 147gr. as the 147gr. Wolf is closer to what the scopes bullet drop compensator is set for. Wolf 200gr. Match would definately be excellent for long range shooting, but the heavy bullets are bad for the gas system- too much pressure. I would not push above 180grs., but even then some think that is too heavy. It would be a good idea to get a BlackJack green buffer for the PSL just in case.
If I hold a SVD sideways and shoot at 100 yards it shoots worse than the PSL shooting off the shoulder. This meaning it is the shooter that causes errors. You can blame whatever you want, be it the ammo or the gun or the weather or whatever. The fact of it all is that the problem is YOU. Period. My shooting coach had to hammer it into my head (and made me shoot 100 yard matches with ball ammo to prove it... I placed the first 5 shots in one ragged hole in the 10 ring and decided that I would rather blame myself for the first messups and then get to take credit for the accuracy).
The US built PSLs usually stink. If there are import or manufacurer markings on the rear sight block, it is probably a US build, even if the reciever is Romanian. If it has no bayo lug, it is probably a ban import Romanian PSL, good stuff.