If you can afford them financially and have time to take one, they can provide some of the best-ever preparation for a certification. That said, boot camps are really tailored for full-time IT professionals who already have some knowledge of and experience with the topics, technologies and products taught in the boot camp. You can't expect to attend one with no prior background or knowledge and emerge from one two weeks later with a certification.
As long as you have a foundation on which the boot camp instructors can build, you'll do fine. Otherwise, I recommend either self-study or regular classroom training to give yourself more time to learn, gain experience, and absorb the vast amount of material you'll typically need to cover to qualify for a certification.
This was first published in June 2002