I am in a similar situation. I have been with Sprint since July 2000, and I have been seriously considering jumping ship to a different provider. My biggest issue is that I have multiple lines and 3 of them are still under contract.
If I could leave right now without have to pay over $700 in EFT I would leave Sprint. I wouldn't put any more faith in Sprint and their promises of network upgrades. I remember going through the same thing with the Wimax roll out. When my market was finally covered I was in the middle of a contract on a device that didn't support the new technology. Then by the time my contract was up, Sprint decided to abandon Wimax for LTE so I didn't want to buy a device that would be obsolete in a few months (that was the timeframe the Sprint reps gave).
Honestly you have to decide what is more important to you... quality or quantity? Right now I feel like unlimited data is useless because it is too slow to take advantage of. I told a friend it is like Verizon is giving you a cooler of bottled water and saying "this is all you get, when it is gone it is gone" and Sprint says "you can drink all the water in this ocean, but you have to distill it before you can drink it" lol
I have been reading and picking up so much info from these forums that I would have never imagined. But with all the different frequencies and varying types of spectrum Sprint currently has, there is no telling what may happen with them. It seems like the wisest thing to do is pick the best network in your area right now, and just come back to Sprint when they finally smooth everything out.