But in the end it seemed little more than an elongated AK.
Yes the PSL is a kalashnikov pattern design, though if you want to get technical it is based on the RPK (Ruchnoy Pulemjot Kalashnikova) not the AK (Avtomat Kalashnikova). The RPK is the light machinegun/squad automatic weapon (SAW) variant of the stamped receiver AK, the AKM. The RPK has a thicker receiver that has an even stronger front trunnion/receiver connection, and a heavier and longer barrel, than the AKM. This is probably why the Romanians chose it as a the starting point for a designated marksman rifle over the AKM.
What else shoots the 7.62x54R?
Excluding the various belt-fed machineguns that fire the 7.62x54R and limiting this to just rifles, other than the PSL the ones I know of are the Mosin-Nagant M1891, the Tokarev SVT-38/40, the Russian made Dragunov types (SVD and Tigr), Chinese made copies of the Dragunov (Type-79/85 & NDM-86), and the Iraqi Al Kadesiah (which also looks like a Dragunov copy, but reportedly uses a stamped receiver and has no parts that interchange with a Dragunov).
There are a lot of claims that the PSL is significantly inferior in accuracy to the SVD, but every credible source (i.e. people who have shot both) I've heard about state that the PSL is at least very close to the SVD accuracy-wise. Dragunov.net has an piece written by a Finnish army sniper who has shot both SVDs and PSLs, and he says their accuracy is equal. This piece is at:
http://www.dragunov.net/finn.html
I've also heard some militaries who use eastern-block weapons prefer the PSL to the SVD as their as their designated marksman rifle, since it is less expensive and requires no additional training on field-stripping and cleaning, to troops who are already familiar with AK/AKM type rifles.