It’s pretty fast, I would say comparable with Delta’s $5 Viasat Wi-Fi. I’ve been browsing and listening to streaming music; Apple Music doesn’t seem to load suggestions on planes which always annoys me.
Have you tried UA's Wifi before? You're kind of getting my hopes up. I remember asking around on FT about what UA's in-flight Wifi was like and I felt like there is a bit of a gap between what was mentioned and what I experienced. Just to be clear, I've used UA's wifi domestically, to Canada, and Singapore and wasn't impressed with the experience. It was only "bearable" simply because there was really nothing else to do except sleep. I hope what you said is true and that B6 sets a new baseline in terms of service. Having said that, I still think the sooner the airlines adopt Starlink, the better!