One of the easiest way to use ETH, even though the UX is still far of the non-crypto standard. Confortable to use, it is simple to manage multiple wallet and to switch network.
Oh, and the interface can be quite slow when cats get stuck in the tubes.
Metamask is one of the only ways for people to interact directly with Ethereum apps at the moment. They have an early mover headstart but will have to work on their UX if they want to stay ahead.