Upwork reviews? Is it worth it, is it safe?

I keep hearing about Upwork as a good place to do freelance work, but I'd like the opinion of the DC community. Have any of you worked on Upwork? How'd it go? Is Upwork safe to use? And most importantly, how much experience do you need to have to work on that site?

At a glance, this seems to be a freelance brokerage business, not a crowdsource design site.

This usually requires a professional portfolio and work references.

At this point in your career you may wish to get more experience here at DC.