It is the best I have used by far. I even compared it to my buddy's Iphone SMS and ISMS and in my opinion it blew both of them completely out of the water.
The other peeps with problems may have to totally uninstall any other sms threading applications they may currently have (can you say... conflicts), coz this one works with the WM (Windows Mobile) SMS/MMS program that comes with the phone. It moves all your current text messages into a SMS Chat folder (located under your default inbox/drafts/deleted folders on your phone, and it also intercepts new text messages coming in.
This app has totally caused me to run up my bill now sending texts. It also has the group sms feature built in as well, and links back with your default contact list to do all kinds of stuff.
The BEST sms app ever made in my humble opinion
. Freestyl users just link it to one button and presto, messages in a bottle, lol.
I posted some more detailed info on it in the Freestyl forum:
http://forum.ppcgeeks.com/showthread.php?t=15518&page=4