I mean... It basically had no competition in the beginning. Also, its SILK codec was pretty good for voice, and without it, Opus would be worse for speech (Opus is basically two different codes working in tandem, SILK and CELT).
When Skype was new it had FREE calling to land lines. My friends and I would make so many fun calls. So many fun times. Then Microsoft bought it and killed the free calling.
Fuck I sat there for a good 30 seconds trying to figure out who Sky PE was...
It wasn't particularly good but when it came out it was the coolest game in town. They just failed to keep up with everything that came after it, and nearly burned it down trying to.
Haven't used Skype for years to talk to friends or family, but kept using it until now when I needed to call some place in my home country (usually banks) by "real" phone call, because support via internet either sucks or doesn't exist at all. Now looking for alternatives...