Like I said, WP8 OS itself is fine, the app works well when they are functioning, but most of the time they do not. Notification is a big issue. Sometimes you get it, sometimes you don't.

Not using Viber, but the last time I tried it, it was ok.

Just keep in mind that with your fund to buy 925, you could have bought former flagship androids (S3 for example) which will serve you well with minimal lags.

After using WP8 for a year, I think that the you really need to love the OS in order to continue using it. There are way too many shortcomings from this OS and you can only justify yourself if you really love the OS.