Honestly, working experience is usually differs from the actual knowledge you have. One can work with
Java for several years but he might not know some important issues in Java.
Study with a certain certificate does provide you an opportunity to know that area more. For me, before studying SCBCD, I just know how can I create, execute and deploy EJBs via WSAD (now it has been renamed to RAD), but I don't know how it works. After studying with SCBCD, I understand WSAD will generate the home/local/remote interfaces for beans to create and interact with different client views, how transaction type/security to be specified, etc.
Thus, in this aspect, I would say certificate is a good mean for you to "learn" the topics.
Nick
SCJP 1.2, OCP 9i DBA, SCWCD 1.3, SCJP 1.4 (SAI), SCJD 1.4, SCWCD 1.4 (Beta), ICED (IBM 287, IBM 484, IBM 486), SCMAD 1.0 (Beta), SCBCD 1.3, ICSD (IBM 288), ICDBA (IBM 700, IBM 701), SCDJWS, ICSD (IBM 348), OCP 10g DBA (Beta), SCJP 5.0 (Beta), SCJA 1.0 (Beta), MCP(70-270), SCBCD 5.0 (Beta), SCJP 6.0, SCEA for JEE5 (in progress)