Yes, on H1-B, you must pay FICA taxes. Your days on H1-B are not exempt from residency. In 2008, you will file non-resident tax return and in 2009, you will file resident tax return.
If you are married, then you can choose to file joint return as residents even for 2008, only after you meet Substantial Presence Test in 2009.
Read:
Your U.S. Tax Return: The U.S. Visas