In addition to what has already been said, depending on your tax bracket now and what it will look like after things like SS and RMDs may enter the picture, a Roth conversion might make some sense as long as you can use up lower tax brackets in 2011 and 2012 to do it. (You make no mention of income or tax bracket so I can't say whether that would make sense in your situation.)
Other than that, I'd tend to agree with Brewer about keeping it in the 401K at least until age 59 1/2 because of the flexible penalty-free withdrawals starting at age 55. If you have room in lower tax brackets you may want to "use" as much of those lower brackets as you can with withdrawals from the 401K -- especially if, again, future SS, RMD or pensions may increase your taxable income down the road. For example, if it's December of some given year and it looks like you'll have another $10,000 "unused" in the 15% bracket, you may want to consider taking out $10,000 and locking in taxes at a low 15% rate on that portion unless you expect to have lower income in the future.