I use their service--I like it. No complaints other than their service coverage is not as large as SprintPCS. The two-way feature is extremely useful, as is their wireless web.
The phone selection used to be really bad, but has gotten a lot better. I have the i85s and find its size to be just right. The have a new model, the i90c (I think?) which flips into an ultra-small size--has a blue backlight to boot.
The only other problem with Nextel is that they're expensive. But worth it IMHO. I hardly ever get dropped calls.
l2c