One of my favorite rendering systems is Kerkythea. The very first benefit of this program is that it is freeware! Also it has almost all features needed for realistic rendering. It even has a render farm which allows you to create a network of computers for fast rendering. The only commercial software that also has this feature is Maxwell render by Next limit. Another benefit is that it has a SketchUp plug-in so you can have both modeling and rendering systems for free. This is very important for me as a beginner architect. I don't earn so much money to buy a really expensive software and Kerkythea was the product that i needed. I fell in love with it.
My clients are satisfied with the renderings so I am satisfied with the program. I'm sure it will develop and will get better and better with every new release.
Anyone who is familiar with rendering can and should try out this software. Especially in these financially hard times it could be an alternative for expensive licenses of well known developers.