Ah, but you would feel the uneveness better with a VFF
As for trails, the rock-blocking effect of the Spyridons made a huge difference. I went on a short trail with lots of hard, knobby tree roots and in my KomodoSports, it hurt when the middle of my arch came down on one if I wasn't paying attention...wtih the Spyridons, much more manageable. All you have to do (even at full tilt) is keep your eyes on the ground up to 15 feet ahead of you - avoid clearly dangerous things like sharp rocks/roots and your feet and toes adjust to the uneven terrain flawlessly.
As stated previously, the hardest part is building up your muscle for them SLOWLY. They will make you want to run further than you should.
All of the injuries I've heard of were people who tried to do the same distances they normally did (even ultra-marathon runners +50km!), or people who didn't adapt their stride and landed on their heels. Without that inch of cushioning, they developed heel fractures.