I've also tried 3D Rad some months ago, there is no trial version for download but they send you one on request. Ive made similar experiences as Tiles and the others. Dont get me wrong, the engine is not this bad, it has the same ODE physics as Gamestudio. But its much slower and lacks many features that you would need for a decent game, like shadow mapping or decals or terrain renderer. But the real problem in my opinion is their concept of predefined objects. This looks like the template concept of Gamestudio but is a lot more limited and inflexible.

Basically, the only thing you can do with 3D RAD is doing mods of their demos. Thats why no one has so far publishd a real game with it since it came out years ago. I have deleted from my hard disk it after playing around with it a while.

But I think, its important that you check out other engines from time to time.