Not many here. Sprint is lavish in giving out great priced plans but suffers from complete lack of roaming on all of its numerous prepaid divisions and mvnos.
And byod is weak also.

Of their many prepaid divisions, only Boost mobile allows byod via Sprint phones with clean esns (and no exclusives like the Palm Pre) and Nextel phones for Boost iden which can use Boost sims without unlocking (with some limitations).

Their mvno divisions are worse. ONLY Platinum Tel has any form of byod at all. Basically you can use other Sprint mvno phones on Ptel but NOT Sprint prepaid (Boost, Virgin , etc). And you have to have the msl to get it on there and may not get data/mms. It has been proven that Kajeet phones can work out of the box with all functions on Ptel by just loading the esn to the database via dealer/master dealer but in general Sprint mvnos have very little if any byod capability.

Sprint mvnos have great unlimited plans and prices but suck eggs on byod and coverage compared to Verizon ones.