Autodesk Certification is not required or particularly encouraged by my employer. (It's officially encouraged, but most managers don't care and won't pay for it.) A few of us are instructors in our company's Autodesk Training Center and we're required (by Autodesk) to get Certified Professional level in the software we each. I would not expect the person reviewing your resume or interviewing you to be familiar with Autodesk certification, but it might help you if you're saying you can use Revit but don't have the project experience to back you up.
There are two levels of certification; Associate and Professional. You can learn by rote to pass the Associate exam (but the text book will be mighty thick) because it's multiple choice with a 70% passing score. The Professional level requires using the software. Being instructor-level in the software, I find the Professional level much easier, but until last year (2011 certification exams), they had trick questions in the Associate exam. You can pass the certification exams after working through the courseware once or twice, but it's obviously much easier if you've used the software. The certification exams cover EVERYTHING you can do with the software, so just being a user wouldn't cover it as there are sure to be aspects of the software you don't ever encounter in your daily job.
I don't think that the Associate-level certification is worth getting without also getting the Professional-level certification in terms of the material tested and the time put in to be able to pass. However, if you're going for both, even assuming you pass on first try, you're at least a couple hundred dollars in. If you're new to the software you'd have to take a class from an ATC and that will run you on the order of $800-$1500 (our ATC only serves our employees so I don't know the fees), maybe less if you can get an online class (new in 2011). However, you can get an entire semester of community college for that price and a free 13-month student license through the Autodesk Student Community website and the amazing BIM curricula that the student community has if you enroll at community college. I think you get a discount on the certification exams with "Student" status, too.