Well, the Holy war was prophesied by Alexandre... :) But I will try to give some insight. In some of the side research I did at the uni, it turned out that actually Illustrator has it completely wrong. Truly, so wrong to the point of expression Joshua Facemyer is reluctant to write ;) ... I've been Illustrator user since v7, uhhh... but I can stop... so, please, no hard feelings ;).
a) The first find was that the appearance of the fill/outline icon indicator in Illustrator suggests those are Front and back colors, which is not the case. They don't have anything to do with front and back colors... Actually, that icon seems to be an in-house rip-off of the Photoshop icon for a real front/back color icon indicator. Maybe someone was thinking that would make a 'consistent UI'?
b) The other thing is that it is unclear why they decided to put 2 color spaces on that icon indicator and then make users switch them. In most cases it was observed that users use, well more than two colors and that the majority of graphics do not have a need to switch those two colors, but to pick the RIGHT color :) As it is now, in Illustrator you have only a 50-50 chance to use the right color, no matter how much you try ;)... So a typical scenario was: User needs some other color, so she/he picks the color. Starts drawing. Ayayay! the outline and the fill are switched! (here comes Joshua's expletive)... So, Adobe provided shortcuts that Chris mentioned, to somehow deal with those two colors, but it feels like a dirty fix for something that seems to be a really lousy UI design. There should not have been a possibility for user to make that error in the first place.
c) one more problem, maybe not relevant so much here, is... that the outline/fill icon indicator and the color mixer often are quite distanced from each other in real world situations. So, you mix color on one end of the screen, click on it to choose it, and the indicator for that change is somewhere else, on a toolbar! Almost no-one bothers to double check to see if the front/back color order is OK. And besides, it's tedious to make such a check every time. The reason is that the toolbar is often moved around, so we don't have a unique place of reference. (Admittedly, advanced users double-click on the outline/fill indicator icon directly to access the color panel, but it's still a bit messy. And, also there is a color indicator on the mixer, but it lacks some functionality, so it gets ignored a lot, and renders one of those redundant.)
We all have some experience on how big companies are trying to make their products cheaper even to the point of jeopardizing the functionality and purpose. From my experience, the UI design departments are no exception. FLOSS has the freedom and capacity to use the good existing solutions and develop new, better ones. There is no need to always follow what the big guys do. ...
So, one really simple solution for the 'user awareness' of the loaded color would be to put the color indicator directly on the tool cursor. even a small patch not bigger than 4*4px would give enough visual feedback and get rid of a much bigger piece of screen somewhere else. For example, when you take the rectangle tool, the cursor icon on the lower right changes to indicate this tool choice, right? Why it wouldn't indicate the color, too? So that you can see: a red circle, or a green rectangle... It would be OK semantically, since the purpose of that little icon by the cursor is 'reference'.
Considering the UI suggestions shown, I really like all that was written in the Wiki, it is concise, exact and smart. The implementations are for a discussion, though. But knowing the 'possibilities' of gtk, they look very good, and a lot of work and thinking has been put in them. All the efforts are great. Speaking of gtk, excuse my ignorance, but is there anything we can do to make this gtk thingy better, or is it a done deal, you-get-what-you-get? Can we create new UI modules? Some modules more appropriate for the purposes here? Or can we switch to something less restrictive? Will this question start a holy war, too? ;) If yes, can you ignore the question? :)
About the shortcuts, there is something that is closer to the way the people think or correlate with the tools and functions. Human brain seems to work much better with full words :) or even with syllables than 1 letter chunks. Words are much better mnemonics than 1 letter shortcuts. Blender 2.5 uses this fact with a beautiful implementation. Providing a meta-shortcut (tab or space or...) user has an access to a small 'command line' like text entry box where she/he can start typing the wanted tool or a function. Tools and functions that are contextually acceptable and that fit the typed letters, show up in a list below the text-entry box. mouse click on the right one activates the tool or a function. It might seem that it is slower to type a few letters than just one. That would be true, but in the long run, not true. How many shortcuts can you remember? And how many function and tool names can you remember? I'd bet more than shortcuts, right? Using meta-shortcut you can access all of them. That is where you save time. Another goodie is that the current shortcut approach and this meta-shortcut approach can coexist with no conflict. If you did not try it yet in Blender 2.5, please try! Just press space in the viewport and start typing... Smooth...
Cheers,
Alex.