Obviously you can't hold this like a regular controller, but the closest thing to it (curling your bottom two fingers to act as support) becomes uncomfortable really quickly.
The (somewhat) comfortable alternative is to hold it like a bowl of soup, using your ring fingers to work L2/R2, and your index fingers to work L1/R1.
The biggest problem, however, is button sensitivity. It takes heavy pressure for buttons to register at all, and the directional pad is even worse in that regard. Trying to use the Stalking mode in Metal Gear Solid 3 requires extreme force, and it's far too easy to put away the gun before a shot (something that was actually made more difficult in the third game). Digital steering in Ridge Racer V, parrying in Way of the Samurai, and pulling off special moves in VF4: Evolution have all been made even more difficult than ever before.
To put it simply; this is a drinking game controller.
