Just a little info I got when I bought my Pila charger, I couldn't get it to charge any of my batts to 4.2v. After doing some checking, I was told by the seller, a knowledgeable person on batts, that the Pila is designed to charge to 4.16-4.17v rather than the full 4.2v. This shortened slightly, the run time between charges, but lengthened the life of the battery. Just something to think about.
In that link I gave you for the TF-001, it was mentioned that with the TF, you are the QC insp. I don't like that, and don't know if the WF-188 is any different. I haven't had any trouble with mine tho.