I'm slowly making the transition to 500px. I just got an account two days ago. You can only upload 20 images a week, unless you have an "Awesome" account, which is equivalent to Flickr's Pro account (only much more expensive, poo!). Ah well. The site design is pretty sweet though. It's so easy to browse and find great work.
Check out some of the people I've favourited already, they're so freaking awesome!