Sean Hollister for The Verge reviews the Logitech PowerShell and Moga Ace Power:

More importantly, the PowerShell and Ace Power aren’t very good at their job. The primary thing that these devices add to the experience is directional control over your games. There, Logitech fails miserably. With only a single D-pad to serve that purpose, Logitech’s job was to make that D-pad the very best D-pad it could possibly be, and it’s nothing of the sort. It’s annoyingly hard to press, and crunches when you roll it around. In games where you need to hold down a direction to keep your character walking, like Bastion and Limbo, it’s literally painful to keep pressing hard enough so the controller actually recognizes your input. On the Moga side, the sliding analog sticks and a lighter D-pad make directional input much easier, but the buttons are tiny and not well built. The triggers squish rather than having a satisfying pull, and the important A, B, X, and Y face buttons don’t reliably activate unless you press them firmly and carefully every time you use them. For $100, these gamepads wouldn’t be acceptable even if there were a library of iOS games that worked well with controllers.

Even if we had a controllers that are actually decent, they introduce a lot of friction with little added benefit. Companies making these things are asking customers to make compromises just to play a game. If you have a case on your iPhone, you’ll have to remove it before snapping your iPhone into what’s essentially another case. With wireless controllers, you’re asking people to carry around an extra accessory. The point of gaming on mobile devices like the iPhone is that you already have this thing in your pocket that can immediately sate your boredom. The best games don’t rely on virtual inputs, and instead make use of the touchscreen as a direct means to manipulate what’s happening on screen. These controllers are maybe beneficial for ports (publishers trying to make a quick buck on nostalgia), but the majority of games people are playing on a daily basis aren’t even asking for these controllers.

I’m also disappointed in Logitech. They have a great lineup of peripherals for PC gamers, but they really fell short rushing their PowerShell to the market.