I have owned 2 mak-90's and consider them the best ak for around the $500 they still run.
Much better fit and finish than the Romanian ak's. I have not had the opportunity to compare them against the zastevas though.
MAKs have a thicker barrel and receiver stamping than standard, are chrome lined, and are likely to be assembled correctly.
They are commonly found at gunshows and online auction still, Even after the money ($150 or so) I spent on converting the one I have now it's been 100% reliable and is easily soda can accurate at 50 yards.
Although converting a Saiga would be my next AK, just for the sake of having a "Russian" AK.