Yes Excel lately is turning into a really compelling product, using functions such as sequence (dynamic arrays), lambda (pure functions) and let (defining sub-variables). You'd think you're coding in a pure functional language, and that's great! Now, ff only Excel had a convolution function! But nonetheless it's a great GUI, everybody knows how to use it and sharing it is dead simple.

The one downside I can find is the lack of a good plotting library. And yes comments as well is something I miss a lot.