Third, the TSP has some of the world's lowest-cost index funds. *Unless you're choosing all-Vanguard taxable accounts, you'll be paying more in expenses than I believe the flexibility is worth. *Plus you'll be losing the benefits of tax-deferred compounding.
I agree, the TSP is the lowest cost 401k plan. I plan on keeping my money in the TSP after I retire, then rolling into a Vanguard IRA right before I want to begin withdrawing.
My only complaint with TSP is that it isn't very flexible with the withdrawals. If the market gets hammered, I may want to withdrawal less that particular year. Unfortunately, it looks as though I would have to take fixed amounts out.
So, I'm thinking that I will eventually go with Vanguard and take the money out as needed.