moving to MySQL 6.0 is a good move? what is most important issues and cautious we have to do before upgrade to MySQL 6.0? 

How do you do the upgrade? setting up a new slave and do yum upgrade? what is the best way to upgrade with minimal downtime?
Moving to MySQL 6.0 is highly regarded as a bad move by most people, as it only briefly existed on the control version system of MySQL A.B. plus some very unstable alpha releases. MySQL 6 promised too many features to be able to be delivered, although some of its features were later ported to 5.5 and 5.6. Others, like SQL-layer foreign keys or the Falcon engine never saw the light. The order is more or less:
5.0, 5.1, 6.0 (not released), 5.4 (not released), 5.5, 5.6, 5.7 (not yet released)

You can watch the story by yourself, recounted in first person by a former employee on this video.

Regarding the upgrade (assuming you really meant 5.6), having a minimal HA setup is a must. I wrote a more detailed guide on a previous question, but every setup is different, and all potential problems are too many to summary in an answer, even between 2 specific versions of MySQL.