So, here's why I liked google voice (I no longer have it because the MMS thing was such a pain.)
Can text internationally w/ only wifi
can text from computer
can check voicemail from any device (and it's much better than any other VM service)
can send/receive calls from computer and it's the same number as my cell phone
easy to record calls
can make VOIP calls from phone (or at least you could, I think google since blocked this)
Yes I know there are ways around most of these but google voice was a pretty easy way to do it.
There's talk that they'll merge google voice with hangouts, which is such an awful application. Couldn't they have just copied what the iphone does? Apparently not, and it's terrible if you try to make it your primary SMS app.