I got this impression as well. I worked on a team two years back building out a very complex Excel plugin using Excel.js. The SDK has quite a few quirks and we

I got this impression as well. I worked on a team two years back building out a very complex Excel plugin using Excel.js. The SDK has quite a few quirks and we ran into some problems along the way, but the team at Microsoft responsible for it was happy to help and interested in hearing feedback and features we wanted. A positive experience :)