I looked into them and decided against.
For me it boiled down to utility. Whilst I have 4 identical 7.4v's for the AUGS, they rarely have similar charge levels on them. So there's that extra step of taking each battery and putting it through a discharge cycle. Added to that when you come to charge the charger will be the limiting factor.
7.4v 2200mAh 5C charge capable. Regular 1C charge is 2.2A. Gang 4 up and you need 8.8A from a single charger, Perfectly possible for some of the better chargers. The charge will take 1 hour. - but it'll take longer if you can't do the 8.8A.
It worked out for me to be more efficient just to have more chargers.
A quad channel charger is about £130, 4 cloned B6AC £100, 4 real B6AC £140. With more chargers I can pick and choose how I want to charge. 11.1 on one, 7.4 on another, fast charge 2C on that one I need right now ect ect. And it gives me at least 1 spare charger for emergencies. The other huge advantage is I know each battery is been monitored. With a balance board the charger can't tell what's going on with any individual cell and may force charge into a problem cell.
The biggest single issue with a quad charger is space management. If you were to say mix up the leads there's a chance you could cause problems. I know Kevin Talbot on youtube has done this by accident and set at least 1 battery on fire on video. If all the chargers are singles the chance of making a mistake is reduced.