Maybe if it was a 5x5 grid instead it would be more interesting. This version you basically have to complete the game twice in a row.
I would expect that to make it easier, although there may be a parity effect of a 4x4. It just seemed arbitrary to stop at 2048 (and I'll increase it if anyone beats it until it becomes impossible). Proofs of impossibility welcome. :-)
So 2048 is too easy?
It was fiendish, but when I reached it there seemed no reason (apart from the game ending) that 4096 couldn't be reached.
Definitely too easy. I got it on my third day of casual play, and it's not like I'm doing deep thought or anything. Just trying to keep the biggest number in the top right, and a full, decreasing right hand row so I can do up/down/right without any danger of messing up.