That depends. I like J2ME, I have fun with it, but I am not going to make it my career just yet. I have had many offers to interview at J2ME companies, but my path it towards Architect and felt that I would be pidgeon-holed in J2ME. I too like staying on the server side. But it also can't hurt, just in th elearning process and understanding J2ME. You might have to build a Servlet and server-side stuff for a J2ME Applicaiton and understanding how it works will help in making the server-side design better.