Does it depend on your service provider? I used the PC software to upgrade mine. Had no issues since but I'm on VDC. OS 5 is really cool. Makes the phone menus etc much more intuitive.
MTN will offer an official update eventually but just download an official one from another network, it only matters if you have to send your phone in for repairs - and you can just go back to the old MTN firmware before you send it off (which is what I did, no one complained about it).
Ya, u can try it out from other networks, there is full guideline from the forum of www.crackberry.com, my brother is using the bold 9000, and he updated the 9000 to a V5,works like a charm.