A lot of people like slide out keyboards, you can easily offer two phone options. Like the HTC EVO vs the Samsung EPIC Sprint offers for Android. Comparable phones, one with and one without the keyboard.
The small screen and tiny hard to use thumboard are killing this device, though. My last phone was the Palm Treo Pro, the tiny thumbboard is a nuisance. There are other phones with similar design who have an easier to use thumbboard. The keys are too small with larger space in between and are too hard to press down.