I bought it on Steam 2015 and I played 1700 hours before I had enough of the related Steam issues back in the days. Been using the Zenimax Launcher since 2016.
Steam is the best. It is fast, it doesn't bother you often and when you need info you can receive a plenty in few clicks.
All other launchers I met are slow buggy mess, which always update something, which threw same ad in your face and force to look it for several seconds etc... Basically if game is not in steam launcher it should have overwhelmingly good reviews, both user and media for me to try it.
Only use Steam because I'm forced to with many games. I've hated it from day one. It's like a side order of sewer sludge you're forced to eat with every meal. It's the ultimate spyware. Fortunately with ESO, there's an alternative.
Steam is great and I’ve only had extremely minor issues with it from time to time in the past, but I have a separate copy I can launch through my game files in case Steam is down and I’m supposed to do a trial or something.
There are just so many benefits to playing via Steam that it would be hard to play without it. I love having hours tracked, playing through my Steam profile, having Steam friends, reviews, badges, player number stats, etc, having payments setup through there and being able to use Steam credit to buy crowns, and having ESO in the same place as my other games, but one of the major benefits is the in-game overlay since it cuts down on significant hassle with alt tabbing while trying to search in TTC, look at set info, etc.