I have the Roland R26
The internal mics are useful in a pinch but does not sound as nice as the Sony m10 or d50 internal mics. I did quite a lot of tests comparing the internal mics to the Sony m10, and the m10 has less noise, better definition/depth.
The R26 directional mics are very directional giving a pretty wide stereo image. They work ok with louder sounds but not that we'll with ambiances.
I decided to keep mine despite this as I like the multichannel recording possibilities, and it was easy to open so I will make a alternative mic front end for my unit.
Either a front rear x/y setup, or I might try it with a tetra style mic.
Mic amps are pretty decent but I have not hade the time to compare them to a sound devices pre yet.