I've stopped using this one and use SKU 1270407 now instead (just a dollar more).
I had the IMPRESSION (can't measure) that my batteries got less capacity after using this charger. I then noticed that at the end of the charge this charger seem to behave different compared to an original Joyetech eGo charger.

First, how a good charger works (if you like you can find here more details: CC/CV Charging):
1) Starts to charge with full output. For a typical eGo charger this is 420 mA.
2) Reaches a limit (let's say 4.15V) and starts to lower the mA output.
3) As the battery cell voltage raises and raises, the charger continuously lowers the output more and more...
4) There's an ongoing change between charging and measuring the cell voltage (so the charger knows where the cell voltage is after an charge phase)

Original Joyetech charger:
You can view the charge pattern described above by watching the LED changing between red/green/red/green/... The red-phases (charge) become notable shorter and shorter which is a good sign.

This charger:
Has even near the end of charge very long red-phases. This COULD mean the charger overcharges the cell, which will do the cell no favor, and could explain my impression of capacity loss. It MAY not do 4) often enough and/or MAY not do a good job at 3).

But... it may be all b*llsh*t, as I can't MEASURE how exactly this charger charges. But at $1 price difference I decided to take no risk on my batteries and bought SKU 1270407 instead. That one behaves visually very similar to my original Joyetech chargers.

It would be cool if someone with the right equipment and knowledge could test this charger (and SKU 1270407) and prove me hopefully wrong.
I've searched Google, but it seems no one did a charge curve test so far.
Btw, http://lygte-info.dk is a very good site with tests for chargers/batteries.