One thing I like about Illustrator(and trust me, there's not much) is the ability to apply rounded corners to any basic shape as an effect. The nice thing about this feature is that you can apply rounded corners with the exact same radius. I realize there are ways of doing this in Xara such as creating a shape that is larger than your desired shape and then using the contour tool but having it as an effect is a much simpler implementation and you don't have to go through the extra steps. I have included a sample pic of what it looks like in Illustrator.

http://www.lucidpixel.com/misc/rounded.jpg