I have a 520 AT+T one that I got for $40 at Christmas , the 521 was $10 more

I have not used it as a phone yet , but I like the Nokia music that you can download for free and listen to off-line but its only a limited amount at once
The GPS maps are one country (maybe region) and it is locked to the first sim card you put in, its $20 more for more maps ,
As a music player and wifi devise it is good , but the battery drains pretty quickly , maybe something is running that I do not know,

It seems that there are no real cheap unlock codes , TMO is better at getting them if you are a customer,

I like the size , one step up from an iPhone , a little smaller than my Google nexus phone

I just bought it because it was cheap and for the offline maps, I hope to unlock it to use overseas and at $40 not care if I break it or get it wet