i actually have a pair of what i think are prototype mics of these

where the tube amp is built into the normal gefell body and it uses an innertube u87 power supply..... not sure how close these are to the current production model.
i would describe these mics as "refined" and "silky" but the silk to me sounds up high not in the (laid back) mid range...... i get great results as a main pair but i usually prefer the sf-24 for that (jazz music) for the thick bottom end.
edit: Just used them on a jazz trio with nice results... Very accurate and wonderful sounding.