Orgmode within and without Emacs, to the very bitter end.

Basically, the same reason for Excel-ops, except in plain text, version-controlled, and almost limitlessly extensible.

Speaking as an average joe indie software builder (nowhere as awesome as Aphyr), for this reason and many others for all my indie productivity / publishing / business operations workflows.

Even if I were to do time-and-materials hourly billing, which I studiously avoid, I can't think of a better base to use. In the cases where a customer's constraints would mandate I work with whatever software they are running, I can, in most cases, continue being org-first and integrate with their system (export/import / upload/download).

My aversion is because, in aggregate, unchecked SaaS-dependence for business operations becomes a part time job in itself, both cognitively and operationally. This is because SaaS means constant changes, small and big.

So I try to keep my workflow mine, and eat the "ick" of the eventually unavoidable "plug in" work to interface with third party systems. Because the third party systems will effectively go away sooner than later. My stuff needs to keep working the way I need it to, to stay sane.

(edit: add SaaS reason, reformat to put excel and orgmode up top)