What are your thoughts on various business models?

The traditional "sell once, offer paid upgrades" seems to be better suited for apps with a stable feature set, where you can take a year or two to produce the next major version. However, a more iterative approach to development doesn't work with this model very well.

The recently popular switch to subscriptions (Adobe, Office, 1Password, Jetbrains, YNAB, etc), while obviously every developer's wet dream, may not sit very well with customers, at least if there's no obvious service being offered (like e.g. Dropbox).