They'll be doing LTE on existing footprint first and then expand coverage with 800Mhz starting in late 2013 after shutting down Nextel. Yeah, everyone wants it _now_ but it's a logistical issue.
BTW, it's Nextel users Sprint is losing and that is no surprise. They expect to lose 30-40% Nextel users by the time iDen network is shutdown. It's in their long term forecast to stockholders. Sprint doesn't really plan a major attack for new users until after Network Vision is complete. It will be painful over next year and they know it.
If Sprint isn't working out during the transition, go to Verizon. Check back with Sprint when Network Vision is complete.