I used to work with Freehand, then I tried Illustrator and while its true that the interface is similar to the one in all Adobe products (a plus for Photoshop users) I have to give my vote to CorelDRAW. Ever since I began working in my current workplace, where the main application we use is Corel I've become quite used to it's interface and to me it has the easiest to use keyboard shortcuts and everything is quite intuitive, didn't take long to learn and now, well, what can I say, I'm a Corel advocate.
For raster work, Photoshop is still king anyway, but I find Illustrator unnecesarily complex and counterintuitive.
This is just my opinion heh, as some people have pointed I suggest you try them all and find which one suits you better.
Just don't use sodipodi
(Just kidding). Anyone ever tried any open source vector illustration apps? I believe there is one called Inkscape or something like that, never tried it though.
See you!