I think the main problem with the UI is that it's not predictable and often inconsistent.

1) Double tapping. I'm struggling to think of another app that uses double tapping (in menus that is). It is of course a useful feature (and I'm used to it now) but double tapping just seems alien on a touch device. iOS apps seem to prefer "hold to x" or "swipe to x" which I think are sometimes very unclear (like how drag and drop often is on OSX, Apple...) but when I'm on a touch device my brain seems to switch modes and expects these mechanisms instead of double tapping/clicking.

2) But now that I'm used to it I constantly notice that double tapping is used inconsistently. For example you can't play a tutorial video by double tapping on it or jump to a ship's location by double tapping on it in the ships menu.

3) You can't seem to reorder the research queue so you need to remove techs and put them back in in the order you want. This would have been a great place to use something like "hold to drag". The queue tab even says "double tap to train skill" but doing so actually removes it from the queue. Double tapping in general seems to behave differently in research since you can select a tech and then tap on it again ten seconds later and it will be added to the queue. This isn't really double tapping per se, but two single taps ten seconds apart. This is a pain in the queue since you can easily remove a tech and accidentally add it again on the second tap.

4) Probes. Fleet menu > ships > probe > go to sector > click on probe in sector > click on probe in left list > click move icon > click up a map level > select sector > click confirm. That's 10 taps for every idle probe that you want to get moving again. Were probes play tested at all?

5) When you click to go to a ship from the ships menu it merely goes to the sector and doesn't select the actual ship which isn't very useful in a busy sector.

6) Why does setting up trade routes work so differently to harvest routes when they're basically exactly the same thing? It would at least save time if you could initiate the route without your ships needing to be at the destination.

7) You can get the zoom level into situations where stuff is readable but the icons under planets are too small to reliably hit. They need some kind of minimum size so that you don't need to fiddle with the zoom level. Another improvement to this might be to not deselect the current selection when zooming.

8) Some stuff is limited by the object count but others are not and nothing indicates which is which. Why can I build two orbital refineries on some planets but only one on others?

9) There is no chat log and this is probably why the chat is empty now. If you could see the last ten lines before you joined a channel then people would be much more likely to join in. How is the current system going to be useful to alliances unless players stay logged in 24/7?

10) Similar to #9, there's no broadcast/announcement log so if you miss the message you can't see it again (except for some where you can relog, e.g. the current patch announcement).

11) Error messages that popup behind the iOS "please wait" throbber. This was particularly bad in the registration form where form validation errors also suffer from #10 so it looks like the server is not responding when really there's a general error message behind the throbber and a more specific form validation error that was only on screen for two seconds before it disappeared.

12) Like most games of this style a lot of stuff is based on the time taken as much as it is on resources available. Except nowhere mentions ETAs for ship movements.

13) There is nothing along the lines of an "empire overview" that shows your stats and graphs of progress which can help you deal with micromanagement.

14) And back to my original post. Icons that depend on text are already sloppy, but if the text is then unreadable on some devices then that's just stupid. I'm still not sure which icon is which, I just remember that left = dest, right = src.