I hear very often about sites who get the temporary upgrades shown on network.sprint.com improve suddenly, but then go back down after time. That is because there are a lot of customers who stopped using data at that site because of the poor speeds. But when they discover their tower is now working again, they start using more and more data, until the site is back to where it was.
In post Network Vision sites with upgraded backhaul, the 3G EVDO speeds should be between 1.0Mbps and 2.6Mbps, depending on sector load. After NV, the backhaul will no longer be the bottleneck on the 3G network. The biggest limiting factor post-NV is carrier capacity.
Robert