Well, yes. After starting a ways back now, and having used to do all of those submissions myself, go with a service. It saves so much time, so much,....... I would still do the main one's myself just to make sure they are getting there like Ezine Articles, Go Articles, SearchWarp and perhaps a couple others. But for mass distribution use a service. The one's that Holly suggests are just fine. You may also check out Isnare, or one of the newer gems I've found is
http://www.articlemarketer.com . They only charge $50 quarterly for unlimited article distributions. If you consider the time you save as compared to the cost. It's so worth it.
Cheers
Davin