I don't know if it qualifies but when casting any spell with an upcast or selection, the spell description window is covering that smaller spell selection and also the top line of the hotbar. It takes a good second to disappear.
The selection window always appears even if there is only 1 level left, but if you don't click something from the selection window it will target a normal attack. Happened more than a few times to me.
The spell description box appears after cursor over, but it would be nice if that upcasting/spell-type selection bar would be foregrounded when you actually click the icon. Or just raise the spell description box so both are visible at the same time. Transparencies for those bars would also help. Not sure why they need to be blacked out really. Maybe that helps with the read, but even like 50% transparency would be nice with multiple windows opening it once if they're going to overlay like that.
In general I just wish I could move things around, so I could place the UI elements where its most comfortable, or for the windows I interact with constantly to be able to move those around. Also sometimes it I find myself wanting to open the inventory or char sheet while still viewing the character or scene. I wish I could move those around easily like other games with a grid overlay. I feel like a lot of nice advancements were made in the MOOs with stuff like that, and it would be cool to see some stuff like that here. Its also nice to be able to quickly hide all the UI elements, so we can try to navigate around just based on the visual cues and stuff presented in game instead of the heads up display all the time