Enligthen is using very similar technique to DRT and it is integrated into Frostbite. I would say that makes used in quite a few games already ;).
And still, calculating radiance transfer can’t be any slower than calculating lightmaps. The difference is I have to recalculate lightmaps every time while, radiance transfer only when I change geometry.
The interesting part about DRT (if done to the paper) is the fact that baking in that case is matter of seconds, because it reuse a lot of data, and cages are generated while baking. It of course lowers quality for anything that is not 90 degree angle wall or cylinder. But it still might be usefull, for small props, which could be contained in simple box, and calculations for that box could be reused all over.
Anyway. I don’t like geometry cages as well. But as I said, there is possibility of reusing work you have to do anyway. Like collision geometry or LOD geometry or just buy yourself Simplygon. It’s certainly far less work than creating unwrap for UV maps.
Btw If you want large terrain I would focus on Landscape Demo. That is large terrain ;).