It shouldn't be, but you should check with your tax person to verify.  It's a tax credit for federal which should be excluded from State.  

The amount of the state refund is taxable for the next year on Federal.  Federal does something with state taxes based on the withheld amount.  Often the two are confused.

I am not a tax advisor; I have paid well every year for the past 33 years to have my taxes prepared.

No, it is a refundable tax credit.  Just like any other tax refund, it is not considered income.

Q: When was the last time you had to pay income tax on a tax refund?

A: Never!

Q: When was the last time you had to pay income tax on a tax refund?

A: Never!

Real answer: When its a state income tax refund on the federal tax forms 

What I believe OP was asking about was if there any possible income tax consequences at both the federal and state level for the $8K first time homebuyer's tax credit.  That tax credit would amount to a FEDERAL tax refund (assuming you receive the full amount), NOT a STATE tax refund.  So to reiterate, I do believe "we're talking about the federal tax refund here."  To be clear, I think we are talking about the refund itself in this post.

Also, what you said about a state income tax refund being taxable on a federal tax return isn't necessarily true.  That would only apply to the extant where you enjoyed a federal tax benefit on that state tax refund.  For example, if you itemized your federal tax deductions and took a deduction for state taxes but ended up with a state income tax refund then the difference between the total amount of the itemized deductions and the standard deduction represents the federally taxable amount of the state tax refund.  Otherwise, a state tax refund is not in and of itself considered taxable income.

Yes, I do understand when its taxable and when its not as determined by income tax filing.  And yes, I left out the clarification on the post as I only alluded to "forms" rather than specifying which forms.  I also left out verify by research on the IRS website and to see a tax professional to see what applies to the OP.  

And yes, this is a ridiculous conversation and yet I'm sure that many will be investigating the nuances of the tax law as it applies to their state tax refunds as it relates to itemizing.