It's a great resource for the movie buff. But a necessary resource for those in the position to hire someone in the business. It's a way to check credits and references. Therefore it's an excellent resource for some one who wants to get hired.
In the TV and film business it's pretty much a sure bet if you want to get hired your chances increase if you have at least a few credits on IMDB. Once you get referred to a composer as a musician or a director as a writer/composer odds are one in one that they'll search you in imdb.com.
You may have some up there you don't even know about it. You can add credits. Or more likely others will actually post your credits while entering credits for an entire project. When I first heard about it I went to check it out only to find out I had a page and was already attached to several films and shows that I'd worked on. Cool.
Once I figured out how to update it myself I began to look up composers that I'd worked with and adding myself to projects that they'd hired me for. If I couldn't remember which projects I'd worked on I would send them a link to their page and ask them which ones I'd played on. This did two things: Remind them I exist and potentially add credits to my page.