i have the verizon service since it first came out several years ago with 1xrtt only. 80 a month unlimited. if you download many gigs of stuff a month, they will cut you off. But you really have to dl tons of videos, music files, very large software distributions to even begin to get close to the magical cutoff.
i use mine in my car. i can connect to the net in atlanta and drive to the beach or to the mountains and never get disconnected.
i get 1mbit (close to ADSL full speed) at times. round trip time is slow though, say 300 to 600 msec.
for those that have the need it is great. verizon has the best coverage, sprint has the same EVDO but not near the coverage as verizon.
to clarify, with verizon, there is 1xrtt (slower, like ISDN) just about everywhere. in many major metro areas, they have the full bore evdo. the card will run evdo if avaiable and 1xrtt if no evdo.