Legitgames.com +++
The game sponsored was Orblisk.
I sent out e-mails to alot of different sponsors and he was the first to reply and showed a keen interest in my game. He made an intial offer of $150 which I negotiatied to $200. He simply asked I included a logo on my preloader, a 5 second intro including the logo and the logo on the game menu, all linking to his website. I also added a "Play More Games" button linking to his site. He replied very fast, and I received payment within one hour of agreeing on a price.
Seriousness ++++
Kyle was very professional, and only asked for a few changes and was willing to negotiate the price.
Money ++++
Orginally he offered $150 but I negotiated to $200. I believe this is very good payment for the quality of the game, which is currently scoring 3.28/5.00 here on NG.
Efficiency ++
Very fast and reliable, all E-mails were replied to within 10 minutes, and I received payment within 1 hour of confirmation of the price.
Social +++
He seemed friendly, and was willing to negotiate.
I personally recommend highly.