Reviews - dbouvier

I've only been working with the C4 Engine for a while now, but I've had enough experience with other game engines, to tell you what things made C4 the obvious choice for me.

Integrity - Refreshing to see an engine tell it straight about needing source code access. Anyone saying different is telling half truths. Period.
Cost - Reasonable price, forever, no upgrade costs, no royalties to further constrain your budget! Depending on your license type you can even have small features added or problems solved for your own needs. For simple problems Eric or the community will normally help over the forums.
Support - Eric is terrific, I can't say this enough, timely responses to questions/problems, new features and bug fixes regularly worked on. A professional and mature community offers its support as well.
Architecture - The design, and the clean thoughtful approach taken to implementing all its features makes understanding and working with it an enjoyable experience.
Features - Regularly being updated, the roadmap shows the few features missing that contenders offer (SSAO, HDR) are being implemented, plus it offers a some things you will only find in C4 like Transvoxel Terrain, Horizon Mapping for example. Being able to request small feature additions, and have a part in discussing with the community and Eric himself the importance and implementation of features shouldn't be under-stated.
Performance - After some stress testing, I'm extremely impressed how far I can push it. It's well designed to let me push the envelope in an organized way.
Modular - Full source and a clean design lets me choose my priorities and extend as needed.
Plugins - Being able to add plug in new features as opposed to replacing parts of the engine allows you keep your game updated to the latest version of the engine without needing to manually merge them.

Extremely happy with my choice of the C4 Engine. If you serious about making a game, take a serious look at C4, you'll be happy you did!