Soo... Time for more feedback?
I would stick to icon and text. This is why I think that way:
Words will ensure that I will have easier learning curve when it comes to meanings of each button (Dan - You estimated that learning every one of them will take You 5 minutes - good for You, but not everybody is as able in those regards as You are - I say 3 to 4 hours for me to learn it by symbols, not by location). With having words next to symbol it will shorten time needed even to only 1 hour. That is huge improvment I would say.
Now - why words AND symbols? Words only would be great... But we should have in regards also another possibility. How about people with dyslexia? They will not like extra reading... Symbol will be their chooise to recognize stuff. That alone is in my personal opinion good eoungh for You to leave symbols be, and just suplement them with words (note - if whole words will start taking too much space, using shortcuts is always an option - not very elegant, but practical).
But there is more into this - imagine You will want to write some hints for game, or training etc. If You will decide to "words only" option, than You will have to use words everywhere in hints. You will propably than have to think of ways to make some words look more important than others - for example using bold words, or curved ones, or in red. And than - which one is best? And dyslexia comes in... And colour blind - so red may be not good way to do things...
But with symbols - with symbols You will be able to use those insted of words. So insted of "In order to begin work on research, go into research section (upper left part of screen) and..." You will be able to have it like that: "In order to begin work on research, go into
insert research symbol here and..." Second instance will try to give me information in first seconds that this is about research (symbol will be recognizable before any word in text). If I will know that symbol already than I will know what it is about in general, and that will be able to make quick decision - read or not read. If I will not know that symbol, than it will catch my interest and will encourage me to concentrate on reading, as it is something I am not familiar with - I will be able to tell that from first glance, not after I will start reading in order to get what it all is about.
For those reasons I would advice You to stay with Symbol suplemented by Words. Of course, what I wrote here may not be representative for majority and... Well... Majority may actually thing completly opposite than that
) with the rest of the graphics style.
Still that is only a matter of learning it while playing a game, so no big deal I think 
