Being able to adjust brightness on the fly would be great. You can kind of do it now by fidgeting with the first three function keys, but that's far from convenient. FN and arrow up and down would be a great choice, I think. And having 5 or so preset brightness settings. I'm also in favor of permanently keeping the scroll lock and caps lock keys illuminated. Having the option to keep them on and change the color when they're on or off in the software would be fantastic.