Where does Just Mobile go after the 2009 release of Gum Plus and its subtly-improved sequel Gum Plus 2.1A in 2012? The answer is Gum++ ($90, aka Gum Double Plus or Gum Plus Plus), an even more powerful and capacious version. On the positive side, Gum++ takes another 800mAh jump in capacity, climbing to 6000mAh from its 4400mAh and 5200mAh predecessors, and once again boosts recharging speeds from the earlier 1.0-Amp and 2.1-Amp models to full Retina…
