Rethinking Your Retirement Rate
(SMART 401K Blog, March 28, 2013) 

"Much like retirement investing, a suitable withdrawal strategy likely will be unique to an individual’s situation. After all, not everyone is going to have the same wants and needs in retirement. A number of other variables also can impact a withdrawal strategy’s success, such as number of years in retirement, other income sources, portfolio value and even asset allocation."
 
The SMART 401K site includes a good spending calculator that shows how long a given level of accumulated savings will last based on assumptions and desired spending levels you specify.  It does not tell you how much you can spend each year, but you can work backwards to get basically the same results obtained using the spreadsheets in my website (small differences result from different assumed timing of withdrawals).
 
As noted in the original article on my site, the actual spreadsheet used in the process is not as important as the discipline required to review results at least once a year and make reasonable adjustments for changes in experience and assumptions.