This is more a list of things I think the devs have in the works or have already considered and discarded, but might be worth taking a look at again, in addition to feedback culled from the forums that I like. Please feel free to add your own UI ideas below.
A- Minimap/Demigod compass - I don't want a big chunky minimap clogging up my HUD. An *extremely* minimalist transparent minimap or even outer screen arrows showing the locations and status (i.e. health, mana, etc.) of allied and visible enemy Demigods would be very useful, less as a navigational tool and more as a HUD perk.
B- Mappable keys - I understand that the keys are being remapped, and that's good, as we have to abandon either map controls or skill hotkeys to play effectively. I know it's going to be a royal pain, but eventually the devs should consider allowing user-mappable bindings, especially as they are targeting competitive play. As a corollary, the devs should consider making almost every aspect of the UI optional, as well as incorporating transparency settings
C- Mouse map control flexibility - this is a minor point, but many many DotA players are going to want cursor edge-scrolling. The Supcom system is fine, but I find the SoaSE (Sins of a Solar Empire) cursor-map interface is a perfect model of how this should work. I know you are having issues incorporating this into early builds, as it won't allow access to editing menus, but please don't forget it entirely.
D- Unit ID - The demigods, at the very least, need differentiation on the main screen. A couple of thoughts on how this could work:
1) Permanent (if clunky) targetable name/level/health/mana bars above each Demi, with color/layout tags showing ally/enemy status, and buff/debuff status. This is bare minimum.
2) Obviously a full SoaSE empire tree isn't going to work here, but if you could select multiple units and have them show on the side of your screen for purposes of status and targeting it would be really useful.
Ex: a large battle developes on one flank, I drag-highlight all units involved, they pop up on my UI split according to faction and maybe class. I can tab through them, and I'm able to keep an eye on the enemy Demis, maybe pop one of them with Regulus' Snipe at just the right time to kill him, or use a stun to interrupt ability usage. Alternatively, I can keep an eye on the health of my creeps, using Sedna's heal to save them before they all go down. I imagine devs already have something like this lined up for when the Generals come into play.
E- Action-Queueing - I have no problem with micro, but being able to queue actions is invaluable. SoaSE's shift-click is one example of how this can work, and it works well with the above-mentioned drag selection process.
F- Quick Skill Allocation - the skill tree is fine if you have the time to use it. In a fierce game, however, it would be nice to have the option to allocate skill points without pulling up a full screen. One way this could work would be to have a small "+" show up in the corner of applicable spell boxes at the bottom of the UI, so that you could simply click on the plus to add a point to a given skill. I know the skill tree is going to get more complex, so when passing the cursor over a skill that branches a small pop-up just above the skill could highlight your allocation choices connected to that skill. Click on one and you've saved yourself the distraction of leaving your Demi in the middle of a battle to select from a large and bewildering tree...
G- Streamlined Item Selection - Having seperate stores for each type of wearable item might have strategic impact on later maps (i.e. boot store is on one side of map and glove store is on other) so I'm hesitant to say that all should be merged into one store. However, if devs aren't incorporating strategic elements, you might consider merging the base stores into one, with tabbed category selection. Additionally, having to sell your currently equipped item before you buy a new one is a bit pointless. If you are actually making any money off the sell you should be able to net that in the new purchase cost, one click, not three...
So just some basics, I'm sure we'll come up with more as the Betas progress, and I know alot of these will be answered, in one form or another, later on in the process.
Peace, Kestrel