MY company uses Vanguard, and overall I have been satisfied with it. However I had a very hard time initially accessing the website. I was locked out, then called and ended up being locked out from phone activation. It honestly took two months (of very sporadic attempts) by me to get online access.
Once that was over, though, I have had no issue. I didn't lose very much over the downturn, so that is a bonus.
I did receive something from them recently which puzzled me. They are offering a fee based account management service. The only thing is, as far as I can tell from reading the literature which they sent me is that they are going to use the same program which you have access to for free right on the website.