I've had my airave since October 2011 and it's made a HUGE difference in service. I live in an area that the Sprint coverage map says has great voice and full 3G, but in actuality I can barely get 1 bar anywhere in my neighborhood, data is deplorable and, often I was roaming in my own apartment. Because of this I had to argue through 3 CS reps before they just gave me one without trying to charge the $120. I do not have it locked down to my number, and i have not noticed any issues with my internet speed - Netflix works flawlessly on my laptop and through my bluray. I have noticed that my phone will sometimes not switch over once in range and I have to toggle airplane mode to straighten it out. Frustrating, but rare.
I would like to know how one of the the previous posters was able to finagle an upgrade out of the Airave line though.