Hi,
I came to US on March 2006 with J1 visa and worked in a University, and then changed my status to O-1 visa on Dec2 007 and work in a company to date. I am wondering if I should file tax as a residence?

Thanks for your input!

O-1 is work visa like H1-B or L1B.
For 2008, you will file resident tax return.
Read about O-1 (read H1-B) tax filing: Your U.S. Tax Return: The U.S. Visas