Hi Tim:

You have received good replies.  Other considerations:

1.  Currently, interest rates are very low.  Immediate fixed annuities are based, in part, on current interest rates (usually 10-year rates).  This is probably not a good time to buy a lifetime annuity if one can wait.

 2. The cost and lifetime income of immediate annuities can be very different between companies (and rates change often).  Accordingly,  it is very important to get current competitive prices.  I used www.immediateannuities.com to compare costs and company strength.  We wanted to buy Vanguard annuities, but we found two strong companies from the above website  with lower premiums (or higher monthly income). We  ended-up purchasing two annuities from them (in our early 80s).

3. All states guarantee annuities--usually up to $100,000. 

4.  This is a link to Bob's Financial Website which has good information about "Immediate Annuities in Retirement":

 http://bobsfiles.home.att.net/AnnuityLinks.html

 Best wishes.
Taylor