I've been using elance.com for some time now. There are both positives and negatives about elance.
Positives: You can often get good quality work for a good price. A LOT of the providers on elance.com are from India or other countries where due to the currency conversion, they can afford to bid a lot lower than US companies for a lot of the projects. Most of these providers also have excellent portfolios and a very good feedback profile on elance (it keeps track of their earnings and feedback earned on the website).
Negatives: As is the nature with outsourcing, since they are so far away, if their communication skills are not good then you can get very frustrated. There ARE those employers who are very bad at this. Some of them offer to stay on AIM, MSN,etc for several hours a day so that they can converse with you in real time, others don't. There are a few providers who try to bid low to catch your attention, and once you've selected them and made a deposit payment, then try to raise up their bid and get more money out of you.
I've outsourced a few logo projects to one provider and I could not ask for better customer service from someone (username - iandistudio). On the other hand , recently I posted a project and selected another provider (username - umerth) and they tried to jackup the price after I made the deposit. I told them it was unacceptable and requested a refund and thankfully was able to get my money back.
Elance does have a dispute resolution policy and it's wise to read up on their suggestions regarding posting projects before you post a project.
Also you should thoroughly look into the person you'd be selecting (by this I mean their portfolio, their feedbacks on elance, etc) and you should have a contract with them. Elance shows you how to do this.
Hope this helps.
