I've had the two batteries and the charger for a few days now. For me, the batteries definitely don't last as long as the OEM battery. With cheap batteries like these, that's almost always the case. I'm getting about 80% of the usage that I get from the OEM battery, so considering the price, they're definitely useful in a pinch or to finish out the day when the OEM battery is running low. The charger is useful, as external battery chargers always are so you can be charging one battery while using another, but it takes forever to charge the QCell and the OEM battery. The voltage is lower than the standard charger, but it seems to charge slower than it should. There's a good chance that it charges slowly in an attempt to not damage the batteries since it's a cheap charger that doesn't have the same controls that the phone has when charging.
For the price, these are definitely handy to have. Don't expect miracles out of them (as you shouldn't out of any cheap battery), but they're certainly nice to have around if needed.