I'm using 4 Tenergy 2600mah pcb cells with a Dereelight DBS 3SD and for fairly long periods of run time (usually 4 hours or more)
I haven't done any formal testing of the batteries specs, however I am getting 1 3/4 hours runtime @ 1.2ah (starting at 4.2v @ 1.2ah down to 3.2v @ 1.7ah) which suggests they are performing to their rated capacity.
They appear to be a quality battery at a reasonable price, but its early days yet with only about 8 cycles, and most of the time I try to avoid full discharges as I try to change a battery each hour when voltage has dropped to aprox 3.6v
I too are interested to hear of other people's expierence with these 18650's