I was in the same boat with regards to TODOs, and I asked myself, given how well steeped we are in technology nowadays - surely this is a solved problem?

Turns out, it is. emacs' org-mode does pretty much the exact same thing WorkFlowy does, only it's tied into all the other niceties of emacs (and to admit that is saying something, I was a vim user). Plus, thanks to Dropbox, and MobileOrg for iPhones and Android, you can sync it to your mobile device quickly and easily.

Each to their own and all that, but I really, really like org-mode. The only reason I've slowed down on it a bit currently (using Astrid atm) is because the Android client is still relatively weak; as soon as that picks up a bit I'll be back on it full-time.