Version 1 of DEVONthink to Go was very much a companion-app
only, and extremely limited at that. The current v.2 (been out for
a couple of years now) is more powerful and useful. I don’t use
it stand-alone myself, but I know that there are users on the DEVON
forum that report they are successful using it that way. Having
said that, if I were to switch to an iOS-only platform, I could
probably substitute Readdle’s suite of apps to meet my (also
basic) needs.