I originally opened up my Roth IRA account with Vanguard in mid-2002. In September 2006, I opened up an investment account with them. Both times I was very happy with how easy it is to open an account and how easy it is to get a customer service rep on the phone to help with questions.
So naturally, when I decided to rollover my 401(k) account that I have at my old company, I chose to roll it over into Vanguard. They have a very easy-to-find phone number on their website and I was promptly connected to a live person who helped me set-up an account online. It took all of about five minutes.
I wish all companies were like Vanguard. They really make everything SO easy! I highly recommend them!