My preface: I'm still relatively new to Elance, and the online freelance communities, so I reserve the right to change/update my answer in another 60 days... ;)
Thus far, I've found Elance to be a great experience. The majority of the Employers that I've worked for have been not only great folks just looking for a cost-effective specialist for their business, but have also been open and passionate about what they do. I love learning almost as much as I love working and Elance has provided an abundance on both fronts.
There are some quirks to the system, but nothing that any freelancer with reasonable business acumen and common sense can't work with. Avoid bad Employers. Bid on jobs that you're good at. Have a long-term vision.
The online application itself, and its associated customer support, has been terrific. They provide an exceptionally easy-to-use platform, and the couple of times I've contacted support, they're responsive and effective.
A side-note: I've tried Guru.com and oDesk.com based on the recommendation of others and been disappointed. I will continue to check them out, but Elance.com is my home nest right now.