There have been many recent developments that demonstrate very high quality assets can be used in the engine. Combine all of these elements and you have one excellent game that can be sold commercially with no strings attached.
The only reason to go with any other game engine is because you have a dedicated team in place that have the time to go through all the hurdles of making media compliant with it.
FPSC isn't just the easiest option, its the best value for money and fastest route to making commercial first person shooters.
I've just downloaded the latest Unity 3D demo which can now be used with Windows and not limited to Mac development which is cool. For outdoor environments it looks very good but its not cheap. $199 for the indie version and £1,499 for the pro version which has all the cool features like dynamic shadows and post processing effects.
http://unity3d.com/unity/download
I like the fact you can purchase with a plugin for iphone development although thats another $499 for the privalege.
Attached is a pic of the editor on my PC and link below shows a video of the demo level.
http://www.youtube.com/watch?v=HruXYhmLB_o&feature=related
1 thing I would point out is that in most other engines you never get any stock enemy assets or AI meaning you can make an amazing environment with shaders but nothing to fight against and no insight into getting anything imported to fight against which is a major plus in FPSC.
The tutorials look quite helpful though. Might give this a go.
http://unity3d.com/support/documentation/video/
Edit - Like the fact you can build as Windows / Mac standalone or for playing in web browser like the new Quake Live.
