First/3rd person Games are very easy to do in 3DGS.
One thing to keep in mind is, 3DGS does use BSP for level building.
This makes indoor areas ideal, such as Quake/Doom/UT type settings veru easy.
Large outside areas can be done, but involves a bit more work as you need to focus on LOD of models, clip range, collision detection, etc...

However, Octave is in the works, so I assume you would be able to choose Octave vs. BSP on a level by level basis?

Octave is much easier for outdoor levels, but I am not saying it cant be done quite effectively now by using some planning.

Peace out, Clay...