Add the ability to use different fonts
Adding latex functionality would also be great, but impractical for some purposes. There are 3 fonts, serif, sans and mono. I am using Ubuntu 10.04 on this computer, and it gives me the options of arial, times and courier, the free ms fonts. The fonts, however, are not arial times and courier. I think they are some of the fonts from my distribution. I installed the ttf-mscorefonts package which installs arial, times etc. from the repositories, but the fonts remain the same.
I personally would like to choose my own font like Freesans or Nimbus, which both are Helvetica clones. When this matter is dealt with, I don't want to have to use Arial, because I dislike it very much and try to disencourage its usage.
The graphics are great with antialiasing, but the fonts.
The places of the text on the color legend also need some fine tuning.