I saw this article on Macworld, How Mac experts deal with their contacts, and I thought I'd chime in.
I've always been pretty good about keeping track of Contacts. In the 80s I had a great little loose leaf binder with small tabs so each person could fit on one small sheet. They could be added and replaced easily and could be overlapped so that the top line (the name) of several would be visible at once. Then I used bbdb in Emacs and then a PalmPilot.
When I first got a Mac I decided I'd use it the way it was intended and not try to make it be like other systems I've used (I didn't want to just live in Emacs). I started using Address Book and it was ok. I learned that it's changed very little since the old NeXT days where it came from and that's unfortunate. There were two things I really liked about it. First was that it was the address book repository and every app that needed to integrated with it. That meant once I put all my contact info into it, I could use it everywhere. Windows didn't' have something like that (you either lived in Outlook or one of its competitors and you didn't use a mail program from one an address book from another and a calendar from a third). The integration with Quicksilver also helped a lot. Second I loved that it let you assign your contact a picture and that other apps would use them, so that I'd see your face in Mail or in a chat program. I always liked that I never picked the wrong John or Mike because I saw their face in the app and while their names were the same their faces weren't.
So on that basis Address Book (now Contacts) did what it needed to and did it in a pretty way. There were some issues. Groups were never great and smart groups had some bugs and you couldn't mark an email address as old. I'd want to keep old addresses around to be able to search for things they sent in the past, but then Mail would get confused and try to send to old address. I've always wanted a way to deprecate an email address and still do (bbdb could do this). (If you use Mail.app and have this problem even after removing old addresses from Contacts, look in Mail.app under the Windows menu at Previous Recipients and clean that out.)
Ultimately having Address Book be my one true source of contact info meant I really wanted an iPhone. I wanted my phone to sync with the mac so that I never had to separately update a phone's address book and could backup and restore what was in the phone. I (still) sync my iPhone every night so I'm not sure what the big deal is in this article. Info about my contacts doesn't change that often that I need it sync'ed more often than once a day. I do use iCloud for it now and I've never had a problem with it.
I have had a problem with the mac's Contacts app and sync'ing with Facebook and Google contacts and just avoid doing that now. I saw duplicates generated and even after I went through and fixed them they would get regenerated. I'm not sure if Mavericks fixed that. While I sometimes use pictures from Facebook in my Contacts I'd rather use a picture I've personally taken of the person. Also I'm happy to have it not change as often as some people change their Facebook image, particularly when they use a pic of their kids (or anything else) instead of themselves.
Like the people in the article I've never used the builtin mechanisms to share a contact card. I've also had no problems adding info in the mac app. I wish the Edit/Done button had a shortcut key but otherwise tabbing between fields works fine. I did setup a template (in the Preferences) with all the fields I want so I usually don't have to use the Add Field function in the Card menu which is annoying.
So Contacts is fine for me, I wish it was a little better but it's ok. It's certainly much better than Calendar...