What should a GUI look like?

I've spent the last few days thinking about what a gui should look like. I stated before that i would really like to create my own GUI (graphical user interface). I can't think of anything that really sticks out as being a must have function. I have thought seriously about how HP have designed the MIE. In my opinion MIE is great for media browsing. I can totally see a desktop running MIE at a party and having my friends browse my music collection, and seeing pictures of my family, but I don't know so much about having my emails exposed like that. Not that I have anything to hide, but it's just a bit wierd. So i was thinking about a GUI with multiple panes, but with different functionality, have a pane for Media, one for Business, etc. Unlike the MIE though I would really want the user to have options. I feel very confined by MIE when I'm testing my themes. I have the MIE installed ontop of Ubuntu 9.04, and one of the things that I like, is that i don't always have to use it. Other times I just have to have it on, but the choise is there. So I definitely want to give that option to the user, even if you have it on, and you just feel like using the traditional desktop, you will have the option. That's about all I have to say on the matter. I would be really interested in what your ideal GUI looks like.

On a side note I installed Linux Mint on my Desktop, I never use my desktop, but i wanted to see what all the hooplaah was all about. Needless to say i think they have a really nice looking theme. So you guessed it, I'm going to butcher it. I haven't received request for any of my themes, which sucks a bit, but I guess everyone is happy with the MIE as is. Oh well. It'll be a passion project. Hopefully I'll have something by next week.