Sprint employee here...can I clarify please?
Sprint is running LTE on 1900mhz g-block, a 10mhz chunk totally clear of traffic today, with a nationwide license. This means that the LTE coverage will mirror 3G coverage eventually.
On top of that, Sprint has roughly 14-18mhz of ESMR (800mhz) spectrum allocated for iDEN users. As that network gets sunsetted, the spectrum will be repurposed for 1xAdvanced, which will allow 4x the capacity for voice calls and 1x data.
Each one of the Network Vision sites will be upgraded with significantly enhanced backhaul, which will provide great 3G and LTE speeds. Granted, Sprint will deploy LTE on a 5x5 configuration, v.s. Verizon which is doing 10x10, or AT&T, who is trying to do 10x10 wherever possible. Difference being, with Network Vision, Sprint is upgrading each cell site, requiring a single truck roll, not an "overlay" like Verizon.
If you look at Verizon's LTE deployment, they are basically adding LTE radios and equipment to their existing sites. Sprint is upgrading their existing site and installing equipment which can run on any frequency, with any spectrum, with any technology. In theory, you'll get LTE coverage exactly the same as 3G coverage, so it will be consistent across the board.
Along with that, there is also LTE rev10 or LTE Advanced, which does spectrum bonding, which will allow a device to use both the 5x5 1900mhz and 5x5 800mhz, for LTE. Much faster speeds with existing equipment.
If you think about it, a device term/contract is 2 years, so you won't be upgrading your phone for at least 20 months, which means any device you purchase today will take full advantage of Network Vision, including LTE. Hell, even our Epic Touchs will get a faster data speed and increased coverage.