I am doing some more testing. Surprisingly my 2010 cells — which are Rayovac 4.0 LSD NiMH rated at 2000mAh — are looking pretty decent according to the charger's Capacity Test mode. It is reporting capacities of 1600-1800 mAh.
The 2008 cells I started testing with — which are Nexcell's EnergyON LSD NiMH rated at 2000mAh — are looking pretty worn out. Many cannot even handle a 250mA discharge, but a few will (but not a 500mA discharge). Those test with capacities of 1100-1400 mAh. Since the Repair mode does a minimum of 500mA discharge, I am not able to try that mode on them.
I did test two of those Rayovac 4.0 AAs using the Repair mode of the Vapcell S4 Plus charger, and neither gained any capacity — in fact both appeared to lose a little. Using the Capacity Test mode one measured 1757mAh and the other 1670mAh. I then did the Repair mode, then after that did another Capacity Test. This time their numbers were 1720 and 1632 respectively. After that result, I do not plan to run Repair mode on any of my other Rayovac cells as long as they measure out with a capacity of 1600+mAh.
I should mention one issue with the Capacity Test mode on this charger; it only partially recharges NiMH cells after the discharge part of the test. So when it shows they are done and 'fully charged' you need to kick it over to Charge mode to really get them full. HKJ saw the same issue when he tested this charger.