Here is a quote from Jason of MaxAmps:
"Balancing is not an issue. Two cells one fully charged one discharged put together in parallel take less than 5 minutes to equal out. We even tested this on the charger as well one fully charged one empty put on the charger real fast and charged away with no issues. Now mix in an old cell with new cells and yes they will have a slight discharge rate difference but with most of us these days running LVC's at 3.4 to 3.5 volts per cell it's not an issue. Trust me guys we did our home work. This isn't something we just tossed together and went with. We have been testing and playing with these for a while now. The reason for the Slash give away was because we used one for the test bed. It works and it works very well.
Jason"