Once you get familiar with the editor, it's very fast to edit charts. It's actually faster for me to edit a chart on IRP than writting a chart by hand on a piece of paper!
Once you have memorized most of the chord suffixes, you don't even need to go to the chord library. You can just add chords directly with the keyboard, which is time saving.
Of course, there's always a few things that could be improved (such as adding embedded rhythm notation fonts, adding a 4th ending, more rehearsal letters, more chord symbols, etc...).
Some people might prefer a simple and basic interface with less features. Others might prefer a more advanced interface with more features. I personally prefer a more advanced interface with more features!