"[I]nvesting via a taxable account can be a sensible maneuver ... most investors should simultaneously fund their taxable and tax-sheltered accounts, and the current tax and interest-rate environment make saving in a taxable account particularly sensible.... [1] Extreme flexibility.... [2] Near-tax-free compounding if you plan carefully.... [3] You can use tax losses to reduce your tax bill.... [4] You may be able to enjoy no- or low-tax withdrawals.... [5] You'll have more control over your tax bill in retirement.... [6] Your heirs will receive a step-up in basis."