Well, you shouldn't file your taxes until you have all your W-2 forms. You should know how many jobs you had in 2008, so if you didn't get that may W-2s you should have held off.
Now, you can do an amended tax return for 2008 that includes the new W-2 information. It is also possible that the IRS will use the W-2 info it has (all of them) to correct your tax return for you and either send you the correct refund amount, or charge you if you owe a balance.
Filing without all your W2's is called "fraudulent tax return". You are required to file a true tax return, meaning you must wait for all your W2 and Form 1099's (INT) before you file a tax return. View the tax return, the section where you have to sign, you are signing that it is a true and accurate return.
If you feel you must file a fraudulent tax return , then once all information is received go back and file an amended tax return Form 1040X
Good luck on your decision.
You need to file an amended 2008 return showing ALL of your income for the year.