I returned my Verizon MiFi for a Sprint Overdrive (not only because WiMAX is coming to my area in a few months).
I pondered jailbreaking my iPhone for tethering (I had tethering working without the JB until AT&T patched the carrier update).
Ultimately however, I found the utility of having an independant device that would work with up to (5) WiFi-capable systems connected at the same time while not getting dropped when I get a phone call quite nice.
And of course the Overdrive has a removeable battery so even though it is only rated at a 3.5 hour life I can carry a few of them.
I chose this as well over the iPad 3G because first, I'm not locked onto AT&Ts network (which is horrible for 3G data in NYC).
Second, 4G is around the corner for all major carriers and now I just need to update my $50 modem as opposed to having spent the extra $130 on a 3G radio I won't use in under a year.
Third, I do need to have multiple devices online at times.
Fourth, I don't want the 3G bandwidth limitations Apple/AT&T are imposing on streaming apps.