While the odd, wedge-shaped design might be offputting, the Guardian finds it a "surprisingly comfortable object to hold," and TechCrunch says it's "cleverly designed, and fits nicely in the hands." It's a little less comfortable in pockets, though -- Ars Technica calls it "the least pocket friendly portable this side of a Sega Game Gear," and the lack of a clamshell means Pocket-Lint finds it "a pain to carry around." But you might not be carrying the 2DS around that much, with the battery life only offering about "3 to 5 hours or of play time" according to CNET, on par with the original 3DS.
It also lacks the 3D functionality of the other models but, unless you're playing Mario 3D Land, TechRadar says it "won't affect gameplay." And that's important, because it's no coincidence that the 2DS went on sale the same day as Pokémon X and Y: This is a system designed to sell games. The lower price of $129, a more durable design, and a lack of eye-straining 3D -- anything that might have caused parents (or budget-conscious gamers) to hesitate on purchasing a 3DS has been stripped away to create a friendlier entry point for gamers to experience Pokémon, Mario, Zelda, and all the other wonders of Nintendo's excellent 3DS games library.