I used to control my finances on a spreadsheet and it was a real pain, I've never had a real estimate of anything, I just got very wrong assumptions.
This experience of using our own software was very constructive, in the first 5 minutes I thought: "how the hell can people use this?", But after a while I noticed that the software is very consistent and it does very well what it is supposed to do.
In 15 minutes I had about 15 ideas of improvements, some I tried to code right away, others, after some thinking proved not to be worth doing, and others gave ideas for future improvements.
Being a user of your own software just brings you benefits, you will know it better than anyone else and be user and developer at same time.
This quote fits perfectly for those developers that treats users as enemies:
"Know thy self, know thy enemy. A thousand battles, a thousand victories.” Sun Tzu
If you write software but don't use it, shame on you!
This post was inspired by: UsWare vs. ThemWare