What do you like best?
Analysis of email signatures works really well and is incredibly time saving. Another killer feature, to me, is automatic syncing: really helpful and easy to use.
Compatibility with Google, Outlook and Office 365 lets the user deal with quite a few different options.
What do you dislike?
A few glitches occured, even if my overall experience was mostly smooth.
For personal use I wouldn't recommend going on paid plans, because they may be a bit expensive for a single "home" user (of course, YMMV based on how valuable the service is considered). Firms could well consider them, of course.
An Android app is much needed nowadays (hopefully it should be available in a short time, as the website claims).
Recommendations to others considering the product
Going for the free version is the best approach, to my eyes: you get the basic experience and can evaluate properly if moving to paid plans is needed and/or worth it.
What business problems are you solving with the product? What benefits have you realized?
It let me manage contacts in a very simple way. I find the email signature a terrific means for this matter and it could be the killer feature (it was for me and I am still using it after a while, mostly for this reason).
It can be really time saving, for a user that has to deal with many contacts.