I love my UHK60v2, and am considering a UHK80. In particular, I like the larger mod and Fn2 keys. But I’ve gotten used to the right-side shift and ctrl keys being nice and wide, and I’m also quite accustomed to using mod+I, J, K, and L for arrow keys.
What do others think about the arrow keys and the overall key layout of the UHK 80? I’ve been waffling about upgrading; there’s nothing I actually dislike about my UHK60v2, and I’m ever so slightly worried that I won’t like the 80 as much…
I felt the same way at first, but it only took about a week to get used to it. I’m a terrible touch-typist BTW. 
TBH, I still use a lot of the same config with the UHK80 as I did with the UHK60 (including IJKL arrows). Don’t forget, you can always remap the extra 30 keys to whatever you want…
And there’s always YUZU/FK Custom keycaps if you want to customize the caps.
mod+hjkl for arrow keys is superb as you don’t have to move right hand from the home row. Personally don’t see the need for the 80 model. If anything, I’d love the 60 with extra function key row at the top 
I still use the MOD+numeric keys for F-keys most of the time. Its less travel to put my thumb down, rather than move my whole hand up.
The F-row comes in handy for gaming though; especially if you need to use F-keys without taking your fingers off the WASD cluster.
I have been using UHK for about 6 years now (started with V1 in 2019 and switched to using V2 in 2023). One of the main reasons I ordered a UHK80 is for the dedicated arrow keys.
In general, I love using the standard mod mapping for arrow keys (and I always miss them whenever I’m using a laptop native keyboard); however, I still find many keyboard shortcuts that use arrow keys as part of its chord awkward using the UHK60. I have tried various approaches to work around this (dedicated key/macro assignments for each combo, secondary modifiers in left side home row in mod layer, vim style arrows using the right half’s fn, alt, super, ctrl) keys, etc) and I find all them to have their own disadvantages.
With UHK80’s dedicated arrow keys, this problem should be completely solved out of the box.
It’s not as nice, but there are alternatives. E.g. on thinkpads I map AltGr+{hjkl} to arrow keys.