21 years ago I used it with Apple’s iSync to sync contacts with my flip phone. Later with my iPhone.

I have some lists set up to sort out family, work, etc. I just looked and this can _finally_ be done on iOS as well. It was a Mac-only feature for far too long.

Inside the Apple ecosystem everything assumes use of the Contacts app, so I’ve never really had to think about using anything else. Back when AIM was a thing, I could use Address Book to add people’s screen names and they’d show up in iChat (AIM is dead, but I still have their old screen names in my Contacts app). It supports adding social profiles, URLs, and creating relationships. I can add their birthdays and they show up in the Calendar. It’s always been pretty seamless and hasn’t left me wanting. It’s been pretty nice, but I wouldn’t call myself a heavy user.

At work I don’t manage contacts. We have Outlook with Exchange and I just use the directory of everyone to send the occasional email. LinkedIn is just LinkedIn; I rarely look at it.

I exclusively use Google Contacts. I have 3 devices and Contacts adequately manages everything in the cloud. It also adequately syncs to Outlook-style contacts, but I barely use anything in the Outlook ecosystem except for email itself.

I find Google Contacts still quite deficient in a few respects:

As with Outlook, it's clearly geared towards personal use (even in the enterprise-class Workspaces) and each individual Contact is meant to represent one individual person who's optionally associated with one individual business only.

This makes trouble for many aspects. I rarely contact individuals who aren't associated with businesses. But within a business, there are usually multiple contacts needed to organize all the departments I interface with. Many do not have personal names or one person! They are, e.g. "Customer Service", or "Billing". Also, many contacts involve Robo-SMS, for security codes, or notifications, and those are paramount to be stored as Contacts, because of their sensitive nature, I want them whitelisted and identified and prioritized properly.

So sometimes I cram more than one contact into an item, with multiple phone numbers/email addresses. But I've found that the tagging doesn't work so well; usually Contacts will "forget" that I tagged them as "Custom - <some string>" and blank them out. And that's uncool.

It is not possible to make folders or containers of groups of contacts (other than tagging them). There is no inheritance or linking of data. So if I have 6 contacts from "example.com" they are all 100% independent of one another, even if they share data. So I must replicate that data and carefully update them all in unison. There's no syncing or associating them.

I don't know any elegant solution for a single app or a single format, that still probably needs to conform closely to the .VCF type exports. But there clearly need to be richer features for organizing and linking data, for ease of maintenance, because I do maintain hundreds of contacts, even active ones, and it's a burden to keep them up-to-date.

The Google integration helps a little bit; it's good when someone's profile avatar populates automatically, or it pulls in data from Maps. More of that, please!