MSN Money highlights the Roth 401k plans:

• Contributions are made through payroll deductions, just as in normal 401(k)s.
  
• But contributions do not reduce your taxable income.
  
• Like traditional 401(k)s, redemptions from the account can start at 59 ½, or after retirement, which ever comes later.
  
• Required minimum distributions begin at 70 1/2, unless the money is rolled into a Roth IRA, which doesn’t require minimum distributions and can pass to heirs.
  
• Any matching employer contributions are funneled into a traditional 401(k).
  
• You can split your contributions between traditional and Roth 401(k) accounts.
  
• But you can’t move money between the different 401(k) types.
  
• Your employer decides which investment options are available to you (unlike a Roth IRA, in which you pick whatever you like).
  
• The Roth 401(k) will sunset after 2010 unless extended by Congress, with no new contributions allowed.