Maybe it's just that I tend to be conservative around my financial planning, but I have never considered the amount you can put into an IRA (Traditional or Roth) or 401k to be sufficient to fund retirement, and so have always also saved in a taxable brokerage account as well.

I would agree with you that there are advantages and flexibility in investing in after-tax accounts and retirement accounts may not have the best investment options. I would disagree that IRA and 401k accounts are not sufficient to fund retirement for some people. A two-income couple with 401ks available at their employer could possibly save $46k in 2013 (2x$17.5k + 2x$5.5k) not including any matching. If both of them are over age 50, they could potentially save $58k in 2013.

PSU