I think it's an above average controller in terms of features and quality, with an above average pricetag.
For people that want something good for PC, it's a great controller to consider if 99$ sits in your price range. However, traditional controllers often work with multiple ecosystems whilst the steam controller notably does not work well as a controller outside of steam.
For me, it's a worthwhile purchase to get one standalone and maybe a second one later when it's bundled with the other steam hardware. At 99$ I'm definitely not buying 4 or even 8 for couch co-op. My buddies will have to BYOD or deal with the drawer of old k400's.