I've argued repeatedly that the current level of credit spreads is a good indicator that the U.S. financial market is not overly exuberant, over-priced, or in another bubble. The market is still priced quite conservatively, and this is not surprising since there are still many problems facing the U.S. economy that must still be resolved (e.g., the huge unfunded liabilities of social security and medicare; the very large federal deficit; the unprecedented expansion of the size of the federal government; the still-large inventories of foreclosed homes, and the millions of homeowners who are "underwater" on the mortgages). We are moving in the right direction, but there is still plenty of room for improvement.
By inference, corporate debt still offers attractive spreads over Treasuries, especially in the high-yield sector.
Disclosure: Author long HYG