I've heard many people complain about the ATI drivers on Ubuntu 12.04. So should i stay with radeon drivers (which im not sure if they are good enough) or try install fglrx and risk getting a buggy system?
The current fglrx release (12.8) doesn't support the Radeon HD 4850 (source). The version included in 12.04 is an older version that does support your card, but you won't be able to upgrade to 12.10 when it comes around.
My recommendation is to stay with the radeon driver unless you need to run a specific application that won't run under it. (And if you do have an application that won't run under radeon, you might want to file a bug so that the features you need make it in before you need to upgrade).