The ability to sign and request signatures from my mobile handset. It's a real time saver and means I can sign documents on the move, and don't need to print, sign and rescan anything.
I bought the app for personal use, but now I use it for anything I need to sign. NDA, property contracts, commission agreements, work orders the list goes on.
It's handy to have all my executed documents stored in the app, email and Drive. I would have to really try to lose anything.
I've used the app for about 6 years. It's got better over time and they have fixed things based on feedback, so there seems to be a good commitment to improve the application even though I bought it a long time ago.
The integration with Drive mobile can be a bit cumbersome, but I thing that's a Google app restriction, not SignEasy. The desktop version integration is great.
They have filled all the gaps in other areas over the years, so I cannot say that there's anything I don't like.