Writing Notes/Dominos apps was my first 'programming' job (if you ignore cutting and pasting random javascript into HTML files...) back in 97. We created a whole suite of in house apps that basically ran the business, including making most of them available as web apps for people who didn't have the Notes Client. It was so fast and simple do to that even a 'dumb' kid with only a high school education and who barely knew how to program could be instantly productive, I honestly can't think of anything that can really match it even today.

I've always been slightly confused why they insisted on selling it as a mediocre email client rather than a quite fantastic RAD tool.