Just my two cents.
Almost all of the old sets I have I bought on German eBay - due to absurd prices in Poland. And I never had a negative experience, although it is common that the sets often lack a few parts (for example 8480 was missing parts for submarine model). That's no problem for me, as I buy sets cheaply and then count the pieces and if I need, order parts from Bricklink. Also, some sets which were described as probably incomplete, were actually complete and even with a few of some other parts thrown in.
And guess what - both sets I bought on Bricklink, which were advertised as complete, in reality they weren't. Although 8485 was missing only that steering arm in the neck of Dinosaur, 8868 had almost no pneumatic hoses so I couldn't even build it until I bought some hoses for making wine or something, and additionally I waited for over a month for seller to send it to me.
So for me eBay > Bricklink, I prefer to buy relatively cheaply and expect set not to be complete and have nice surprises.
Well, let's hope I didn't jinx my luck for sharing that :)