One of the single biggest improvements to Ionic 2 is the way it leverages the power of Angular 2. Angular 2 brings incredible performance boosts, especially to mobile.
Today, an Ionic and Angular 2 app is just TC-39, standards-compliant JS. While it may look different from what you’re used to, the benefit is the entire web industry is moving towards this standard set of technologies, so your skills will adapt to other projects beyond Ionic and Angular 2. That wasn’t the case with Angular 1.