Web Component Developer exam, as name suggests, tests knowledge about designing, developing and deploying web applications using Servlets and JSP. It is more logical to take this exam after SCJP unless you are/want to be only a desktop application developer.
Certifications in general are an opportunity to refresh subject knowledge which in turn help you to do your job in a better way. Of course, they always look good on your resume.
I have been working in Java web development for the past 6 years. When I prepared for my SCJP (new version), in Feb, I was surprised to see many subtle issues that were not on my radar. [ April 17, 2007: Message edited by: Sri Kan ]
I agree, even if it doesn't help you to improve your salary or to get a better job (Which is always a debate), I think it will help you to learn and apply basic skills that even a Senior developer need to refresh once in a while.
It should help you boost your confidence. Don't always think of having something to write on your resume because not all employers are after that. Besides, once you got the job and started working who would care if you're certified? To them, your performance is more important than what's on paper.
Also, don't always think it will improve your salary. Maybe it will, but not always.
I am going for it still because what's important is the review part and a feeling that your knowledge and skills have improved especially if you get a good score. The journey towards there is the benefit, I guess.
Plus, SCWCD makes you a certified "developer" not just a "programmer"