I tried Hangouts for SMS for about a month, but now trying something else because of a couple issues:
1. Erratic behavior when using People Widget for text shortcuts: If I use the widget, it would launch the appropriate conversation. However, after typing a dozen or so keystrokes, the app would "blink" and kick back out to the conversation list. In addition to doing that pretty much every time, it would often crash the app altogether. I don't think it did this before they added to make calls from the app, so this likely will be fixed with an update. Still, really annoying at this point naturally.
2. No search ability: This is a peculiar omission. I don't do a ton of searching, but some threads I may add 100 individual messages or more in a day, so to look up something from a few days prior takes a lot of scrolling. Generally I'll go back to the stock app to search, but again, annoying.
Giving Textra a go, like it so far.