In high school, my friends got onto the Numworks bandwagon, and we even used them on the SATs and AP tests (they were explicitly allowed). To be fair, this is before Numworks locked down their calculators and the alternative firmwares (Omega) died off, but maybe there are jailbreaks now and things are as they were before.
The difference (as far as I know) is that Numworks (and Casio, etc.) are mainly used by students, while SwissMicros (and HP) are used for very quick problem-solving on the job.
There was a time when RPN was waaay better than the TI and other competition, but in my mind that time is now past us. I can use both designs well and will take a TI-89 over a Swiss Micros (mind you I own several) almost any day as it is more straightforward. That's my opinion anyway. This improvement over the DM42 is pretty cool though.
Another Swiss Micros use is for people who work in a lab with gloves and can use a calculator better than a phone.