I bought ESPlanner some time ago and found it very useful. However, it does have its limitations.
The "consumption smoothing" idea is that we're happiest when our standard of living (annual consumption in $ - excludes taxes, savings ) stays constant. i.e. sharp drops cause pain. I buy into this. I have no desire to scrimp and save today and then spend lavishly when I retire. Or worse still, live the other way around!
So, his program figures out your current standard of living (inferred from your salary, investments & savings), your expected lifetime earnings, and then calculates a constant standard of living to age 100. It takes into account SS, RMD, taxes (fed & local), has inputs for special expenses/income (like health insurance & periodic large expenses, inheritances) property taxes, loans etc. It clearly shows what your tax bill will be each year & I've compared it with Turbotax and it is really close!
From that point, it is quite useful to see how your money would accumulate & how you would spend it. Effects of taking SS early v/s late; timing of tapping into your tax-deferred accounts, changing your standard of living, your children becoming independent, moving to another state, a less expensive house etc.
The limitation I found is that portfolio performance is calculated using a constant percentage. This is obviously not the case. I use very conservative performance numbers to overcome this limitation - but it is a big issue in my mind.
The program does have a monte-carlo version, but I haven't figured out how to use the data it outputs in my real-life situation. It spits out a lot of numbers but its recommended standard of living is too agressive. They know this and have said they're working on a future release that takes users risk profile into account.
Larry Kotlikoff has also written a lot of papers that are available on the net. I've found them to be very interesting.
Regards,