Controller support in Steam has continued to improve: supporting pretty much any controller, gyroscopes, per-game custom mappings, sharing/applying community created mappings, etc. I'm not aware of anything similar in competitor's stores.
Library filtering and search is hugely improved over the old system that only supported manually adding games to your own tag categories. "Dynamic collections" can be created which include games based on store tags, genre, controller support, whether a particular list of friends also have the game, and a few other things.
Updates/news for games you own or are following is a lot more visible than it used to be as well.
Same with Steam -- it's just an interface to get to the games. Doesn't need to be obtrusive or detailed, just good enough to help me do what I need it to do.