A lot of people dislike kcalc, and a lot of people don't like the Gnome calculator. One feature I do like about the Gnome one is the insert ASCII value feature. I tend to use xcalc and am generally happy with it. IMHO it's more usable than either of the other two, especially since it has an RPN mode. OTOH, I tend to use spreadsheets for a lot of things that I used to use calculators for.