Indies have been using it a lot recently. Off the top of my head I can only recall Antichamber [1] as a successful UE-made indie game but there are also a ton of small games made with it. You should check out RockLeeSmile's videos [2] if you want to see some.

[1]: http://www.antichamber-game.com/

[2]: https://www.youtube.com/user/RockLeeSmile/search?query=unrea...