Gilsan, I always ask people who pose these types of questions to answer the questions themselves. Tell us about your own experience?
I have about 600 domains parked with Sedopro. Income is $20 to $30 a day, with half of that coming from just 2 or three domains. The best one I paid $1,000 for, and another I paid $500 for. On the other hand about half of the 600 names generate no income at all. Many of the non-earners were typos and odd names that I registered when I first started in this business a year ago, and I will let those drop. More recently I am purchasing names at auction and concentrating on at least halfway decent generics. For example I recently picked up linkeditor.com, mexicocall.com, tilling.org, redland.net (there are several cities called Redland or Redlands) and cratervalley.com (there are Crater Valleys in Nevada, Panama and Africa).
I also have two domains that each get about 50 or 60 hits daily, but no one ever clicks. I've tried changing keywords but nothing works. I may move them to NameDrive or DomainSponsor and see how they do.
Also, let me add that I'm going to start building mini-sites for some of the domains that pay a lot per click. That way I can drive traffic to them with Adwords and try some arbitrage. Actually, I did this when they were first parked at Sedo, not knowing that it was against their TOS (a real newbie move, I know) and I made $200 a day profit until Sedo told me to stop.
I do believe the improvement is due to better keyword selection as many of these names are parked at sedo where I have spent some time getting to know their keyword optimizer. Hey, if I can double my portfolio to two dozen names maybe I can get into sedopro one of these days? 
