Ugh, I hate that SMS is conflated with Hangouts as it is. It causes notifications for work-related chat to get mixed in with notifications for personal text messages on my phone. Can anyone suggest alternative SMS clients for Android?
TextSecure! Nobody I know uses it, so the encryption/privacy features are basically useless, but it's a fast, well-designed, pretty app regardless. It also has a feature I love: persistent notifications for unread texts.
Seconding this, switched to TextSecure when they combined SMS and Hangouts. It is an excellent SMS app replacement. The crypto doesn't get in your way, even when almost none of your contacts also use it.
I love Handset SMS! I never use anything else once I found it! You can customize the alerts you get, icon/vibrate pattern/sound and other features as well.
I'm quite a fan of Hello, but you need to explicitly turn off a "feature" that tells people you message you send it with Hello. I have no idea why they don't just charge a dollar for it.