I'm not so sure. I've had numerous problems at this point including breaking bugs where games simply wouldn't launch or install. Also, the game management ui is pretty poor by modern standards. There's no way to sort/filter by play time, genre, or any other qualifiers that would make it easier to select a game to play. I imagine after all the sales, big picture mode, and steam os there's a huge need for a better, more fluid UI. The current version is pretty antiquated these days. To put things in perspective, there are open source MAME UIs that are better now.

Could you point me to some good examples of those open source MAME UIs? I want to show them to someone who wanted to build a game grading web page.

I mean, it kinda sorta does? Watching trailers for games is agonizing through the Steam client, even using a pretty beefy PC that can play the games themselves just fine. When I go to the Steam website instead, the trailers play just fine.

Steam seems to deprioritize it's foot stamp when it's not in focus which is why you might find the videos to get choppy if you happen to also be multi-tasking. If you focus the client they work just fine (at least this is my experience.)