What happens when you get out of a 4G area? You need to fallback on a solid 3G network, not a crappy CDMA one (speedwise, coverage is good).
ATT 3G HSPA+:
According to Engadget, the upgrade could realistically offer most users download speeds between 7.2Mbps and 14.4Mbps.
Verizon '3G':
(wikipedia) On June 30, 2007, Verizon Wireless had completed the overhaul of the entire EV-DO network to EV-DO Rev. A. This enables PC Cards and certain phones to obtain theoretical peak download speeds of 3.1 Mbit/s and upload speeds of up to 1.8 Mbit/s. [11] The actual download and upload speeds vary due to a number of factors, and users will typically see speeds close to 1 Mbit/s down, and 500 kbit/s up.