Hangouts is great. It unified all the google chat apps
First thing first there is a difference between google apps and core android apps. Hangouts was created to solve google chat issues. Hangouts is more like G+ messenger than it is Gtalk. G+ messenger didnt have away/online indicator and it had MMS support. People always seem to confuse google apps with android apps. They are not the same team. Google voice is incorporated at the moment in bits and pieces. Google voice numbers have been ported over to hangouts. The SMS app is not a google app. Hangouts didnt only replace Gtalk it also replaced G+ messenger. Hangouts is used by google employees also. If you dont use google+ then it look like hangouts didnt solve anything. They connected gmail contacts, Google+ contacts, android phone contacts and Google voice hence the long list of contacts. Hangouts is aiming to be whats app not Imessage. Google is all about cross platform. Hangouts is available on IOS, chrome and android. How is not better than GTALK. How hard is it to type in the email, number or name of the person then hit send message or video chat??
The issue we all had was that G+ messenger was not available on the web. GTALk inside gmail was different than the GTALK mobile app. We used our google voice number to make phone calls via GTALK. We didnt know which app was doing what. Now those issues are fixed. On the google+ web We had to use Gtalk to chat with G+ users . When we went back to the g+ messenger app on mobile the convo didnt sync over. It would a clash between g+ messenger and gtalk. Not every user was available on gchat.