Skype's various mobile apps are by no means perfect. Call quality varies dramatically, especially in video chats. The interface can be a wee bit convoluted, particularly in the desktop Mac client. Skype has been around for 10 years, however, and it has a huge user base. If I need to have a video chat or share my screen with one or more people, I almost always use Skype.
Google Hangouts is another great, if imperfect, option. It's a full-featured video/chat/communications program available as Android and iOS apps, as well as a Chrome browser extension. Unfortunately, a lot of people I try to connect with via Hangouts sheepishly admit they've not used Google's chat service before -- which means we end up Skype-ing.
There are plenty of other messaging and communications apps available, including Kik Interactive, Snapchat, TangoMe, WhatsApp, Facebook Messenger, and Line. So what does Wire offer that's new and different
Wire's most striking differentiator is probably its interface. Its look and feel are so extremely minimalist, it's practically a parody of minimalism. There are very few visible options and buttons to tap. The overall look is dark and borderless, and it has accent colors you can choose. Put another way, Wire reminds me of trying to find my way along a dimly-lit W Hotel hallway. The hotel had a notable hipster vibe, but it lacked any sense of user friendly practicality. (It's nice when you can actually find your way to your hotel room.)
After installing Wire, you choose a photo for your avatar. You can either take one using your smartphone camera or choose from the camera roll. I picked a photo taken a month ago. In the picture, I'm on a balcony overlooking a sunny South Carolina beach. Wire, however, won't let me position the photo so that my face is in the app's frame. All it shows is the beach, so I used a selfie instead.
To initiate a call, you give Wire access to your contacts. It looks for people in your address book who are already on Wire. In my case, it found only two -- coincidentally, both are tech journalists. Then you drag down from the top of the home screen to perform a search or select from the list of contacts you already connected with. None of this is intuitive, and I recommend reading Wire's online help page before getting started.
Voice calls, in my experience, sound clear and the connections are stable. I haven't used Wire enough to definitively compare it to Skype or Google Hangouts, but overall, you get as good if not better audio quality with Wire.
Wire also has a few other nifty tricks up its sleeve, including the ability to share photos, YouTube videos and SoundCloud links in conversations.
As of its first version, Wire does not offer video calling, and it's not easy to determine if messages are sent. Also, because it's so new, you won't get much use out of Wire unless you can convince others to install it.
With all the other communication apps available, I suggest taking a wait-and-see approach to Wire. It needs time to grow a user base and hopefully make its interface more intuitive.