Spreadsheets are hard to do and even harder to do right, so congrats on launching—although given your backgrounds I don't think you ever lacked the manpower to let this be a technical challenge ;-)
My initial reaction:
* It does feel pretty fast
* but spreadsheets on the browser always represent an inferior UX
* the data tables / formula tables are a solid idea
* no self-hosting outside of Enterprise makes switching to this harder than it ought to be
* limiting the free plan to 3 sheets feels like a strange decision