Without experience, certification is nothing but a piece of paper.
I was once an interviewer attending a group meeting (3 interviewers, 1 interviewee). The candidate was quite academically strong. He was a teacher as a SCJP instrutor in a private training school. The tricky questions I prepared were nothing for him. But he didn't get the job. Three of us unanimously agreed that he was not qualified for the position. He only had teaching experience, didn't have actually development experience. The company needs somebody to code, not a guy to teach others how to code.
The moral is a piece of paper won't give you a job from nothing, but it does give you a better job in terms of remuneration. [ October 22, 2006: Message edited by: James Quinton ]
communication skills are a must to get a job too. Especially if you are applying as a fresher, SCJP might help you to get interviews and even do well in them. But since you are a fresher (and interviewer does not expect you to be as good as a experienced guy technically) communications skills is what will give you an extra edge.
If you are looking for entry level positions I am sure it will be a lot of help in securing the job. For one, you will have much better understanding than those who didn't take the exams and will help you answer the questions better. Two, it will also improve your confidence in taking a new challenge because you have the SCJP in your hand.
For experienced positions again if you competing against a person without a SCJP certification you can get the leverage as well.
The interesting issue raised by the comment by James is that if everyone must have experience in order to get a Job as Java programmer, how does anyone get the first job if they have no previous experience. Kinda tricky isn't it.
In reality of course, some employers will take on inexperienced programmers, and when making that decision they will factor in academic experience and commercial qualifications such as the SCJP. However if your entire experience with Java is purely from studying for the SCJP you are very unlikely to be offered a job.
A more typical scenario for getting a job is an academic IT qualification e.g. BA degree in a computing related discipline, an industry qalification such as SCJP and some contribution to a real world or significant appliction.