Hate it. Let me elaborate:
1) Inconsistant UI – Previously, you knew that touching a persons name would take you to their contact information. That was sensible. Now, touching their name takes you to their contact information, unless it calls them. Now I have to remember the context of where the name appears in order to know what tapping it will do. Likewise, everything is built in, except where it’s not – and it seems like there’s no consistency to these decisions.
2) Lack of Hubs – I get it, they’re hard to maintain, and aren’t feature rich. But they’re *amazing* and what differentiates WP from iOS. If I want to open an app to post an update, I’ll use an app-centric platform and go to iOS.
3) Most of the “updates” aren’t. Games, Music, People hub, bluetooth… everything took a step backwards with 8.1. If I could use WP8 with Cortana (which doesn’t integrate with Bing rewards) and a notification center, I would be happier. I’m aware that a lot of this is because it’s not final software, but it’s annoying all the same. And Bing Vision is in a terrible location.
4) Lack of polish – The whole UX just “feels” less polished. There’s nothing wrong with it, per-se, but I don’t like it as much.