Went to the Sprint Store this morning and ended up talking to the store manager since the tech guy was busy with another customer. He verified my phone worked ok just standing there and it actually got a great 4G signal and was VERY responsive.
He said some others had complained from 'up north' where I live (about 5 miles north of the store - Cypress (Houston), TX). He said they were installing LTE in the towers up there working their way south. I said why would my 3G performance suffer if they are installing LTE?? He said they are doing hardware and software mods to install LTE, make some software changes to 3G, and remove the Nextel stuff all at the same time. So that's why a tower could be out of commission for a while. For me that while has been about 3 weeks since I got my new phone.
I was thinking I might find that damn tower near me and stop by sometime when a truck was parked there and go talk to the guy. Might do that...