I also found that SS office, DMV, bank, etc was relatively simple to do. I didn't use a service and I would advise against. You still have to be the one to stand in the line, no need to pay someone to organize your paperwork. The biggest pain has been my office. I switched my maiden name to my middle. Whoever changed my name in the system was super lazy and just added my new name to the old name, and now everyone thinks I have a compound last name despite the lack of hyphen. Sigh. It's been 3 years. People still call me by the wrong name or alphabetize me incorrectly!
Just wanted to note that, contrary to what PP says, getting a new passport with your new name is only free IF your current passport was issued within the last year (see
http://travel.state.gov/passport/correcting/ChangeName/ChangeName_851.html). My passport was about 1.5 years old when I got married. I had to pay for a brand new one.
I have a few things I have never switched. Notably student loans and a credit card to a clothing store where I buy most of my clothes. My work credit card is also still in my maiden name. I made sure that all of my new documents clearly spelled out my middle (maiden) and new last name, and I've never had any trouble explaining that something is still in my old name.