Been using the Ultra all day and its safe to say I'm extremely happy with it.
Screen is amazing, and I've not even checked out QHD yet. It's just a beautiful thing to look at and use.
Once the phone is setup, it has run cool and feels very fast and fluid.
I thought I would hate OneUI coming from a Pixel, but I'm very pleasantly surprised. There was some bloat to battle through, but overall its minimal, but the sheer wealth of options, especially with the likes of Good Lock (as suggested by
@smokedog thanks for the tip off) more than makes up for it; I was delighted to find the transparent navbar option in Good Lock, thats always something that annoyed me with the Pixel UI. Also, going from screenshots, I thought I would dislike the UI, but when you actually see it on the stunning screen and use it in real life, I actually think I prefer it in some ways to the Pixel UI, after a little bit of tweaking in the settings. It somehow just feels more fun to use.
Feels like a premium product, surprisingly good haptics, certainly better than either of my previous Pixels but probably still not quite up there with the iPhone there, but still satisfying and not cheap feeling.
A couple of surprises has been the finger print reader, which is fantastic for me, way better than the rear mounted Pixel readers, secondly, the built in keyboard somehow seems way better than gboard did on the Pixel.
Finally the camera, I haven't really got any amazing photos to share, but can confirm the pictures are extremely good all the way from 0.6x to 10x. Having never had a telephoto on a phone before, only on compact cameras I owned and stopped using years ago, I am blown away by it. The 10x lens clearly seems to work better with decent light, but overall, the camera experience is seriously good.
I've not tried the freebies yet, but even though I never thought I'd spend £1200 on a phone, I actually feel like this might actually be worth it. First upgrade for ages that has actually seemed like a properly good upgrade, which is great considering how underwhelming going from the 2XL to P5 was. Very happy so far!