The 457 is an interesting investment. There are two main question I have:
1.) Is this a government 457 or non-government. I ask since if a non-government plan (I have one at my non-profit hospital), then the assets are not guaranteed and can be at risk if the organization goes into bankruptcy, etc. It's rare, but it does mean the assets aren't really "yours" - even thought they come out of your paycheck - until you leave the job. It's kind of strange. But the government plans are protected.
2.) What's your tax bracket - If you are higher now than you will be down the line, then it makes sense. I have a combined tax rate of almost 35%. My plan charges a 0.31 management fee. So if I max it out at 18k per year, I save a little over 6k in taxes while I pay about $60 a year in fees.
Finally, the 457 is interesting in those considering early retirement. When you leave your job, you can take the 457 money out of the plan without an early withdrawal penalty. You do pay the income tax, but you have instant access to money, almost like saving for your own severance package...
I contribute to a non government (so not protected) plan, but feel the benefits outweigh the negatives. But I might get nervous if I hear the organization starts hitting some rough financial times..