I've been using this for a while now ever since Mel sent me a copy. It's awesome. The UI is intuitive and it does what it says very elegantly and simply. Nothing fancy.
Love the Auto-reply (someone FINALLY implemented this in an actual product) and Backup/Restore. I'm sure a ton of users would like this feature. So many times we lose all our SMSes just because we have to upgrade to a new version of the OS.
Get it now : http://www.trinketsoftware.com/powersms/