I have been an SMT 5600 owner for 3 years now. I bought this phone off of ebay for a fraction of the price it was new, and I have never looked back.
Let me begin by stating how incredibly robust this phone is. I have dropped it onto concrete intentionally to show my friends how much more well built it is than their blackberrys. This phone is an older model, thus it can only transmit and receive data on the GPRS signal, but it has all the standard features any blackberry has.
I have used this phone as an MP3 player on roadtrips, and there is loads of free software available for this phone which improve functionality such as watching movies, television, or browsing the file structure of the phone.
I will issue my only complaint. When using the camera to capture video, due to the placement of the microphone on the camera, you cannot capture sound that comes from any direction other than directly behind the cameraman. This means that most of your videos will be silent, or rather faint.