Blackberry: SMS apps

Hiya :)
So today I upgraded my software to OS 5 which is all fine and dandy (apart from the fact most of my games have gone AWOL :().

However, the app I used to use for SMSing isn't compatible with this OS, and quite frankly the in build one is ****. I've had a search around app world and the internet but can't really find any good recommendations. I was just wondering if people use any good ones or know their friends do.

is there no way of downgrading until this app is compatible with the lastest OS? I'm not a blackberry person so I don't know an awful lot about them.