i think the Nokia's over there use PersonalJava?
the nextel phones can only handle MiDLets. I've installed various apps i tried on emulators to the real phone, and they all work fine. i'd say one possible difference is the fact that the nextel phones are a heck of a lot less powerful than the emulators that i use (sun wireless toolkit emulators), so i pay attention to the VM speed in the emulator and set it to what the phone actually can handle to get a better feel for how fast an app will run on a real phone.
in fact. here's my phone with blazing boards running:
nextel phone it's black and white, but i'll probably get some higher powered color phone soon.