Yeah I read that in the reviews. I'd have to get a dual chemistry charger. Reading the reviews they seem hit and miss.....then again the reviews for the supposed factory batteries were hit and miss.
If you currently have the NiCad C3 batteries, and the charger that came with them is the black one, then it will probably not charge any Lithium Ion batteries, regardless of brand.
If you want to move up to Lithium Ion batteries, and you have to buy a charger that can charge them, then check out an actual Craftsman LIon battery and charger combo kit. You can find those on sale from time to time and the combo kits will only cost a few dollars more for a charger and a battery than just the charger alone.
But to answer your actual question about if anyone has any of the off brand C3 LIon batteries and how are they, then I can answer that because I have one!
I bought a "compact" version of the C3 battery from a Jipo-Japo maker about 5 years ago to use in my Craftsman C3 Hedge Trimmer. The trimmer came with a NiCad battery and that only lasted about a year. I had an Amazon gift card that someone gave me for $25.00 and I used that to buy the Jipo-Japo compact LIon battery for $18.00.
I figured for that price, even if it lasted a year it was worth it. I already had several Craftsman brand C3 LIon batteries and dual chargers, so I was good to go there and didn't need to buy a new charger.
The cheap battery lasts longer than the Craftsman NiCad one every did on a charge so I am happy with it. The main difference between the Jipo-Japo battery and the actual Craftsman C3 battery is that the Jipo-Japo battery does not have the charge indicator LED's on the front of it and there is no LED in the stem of the battery pack that normally lights up the "C3" logo on the tools.
Other than that they are the same color, same size, have the same size and shape charging contacts, and even have the same semi-rubbery parts on the base of the battery.
Jim