WHat the best os available and where can i get it. Im have tmobile service in NYC

A very good question. Some people like to use the latest version available; some prefer the one from their carrier. I don't think there is a "best". T-Mobile's 8700gs come with 4.1.0.284 (I think). I know that the one from Telstra and Bharti are new.

To download and install new version, look here: BlackBerryOS 4.x Download FAQ - UPGRADE DOWNLOADS

Good luck.