I've recently subscribed with 500px, looking for alternatives to flickr, just in case they decide to pull the plug on their service.
500px was able to quickly attract many photographers to showcase their work, and have it rated by fellow photographers or members. Visitors can like a photo, add it to favorites, and comment. All that will be tracked for a photo, and people will be able to see how much it's liked.
You can create a portfolio with different sections (called Collections). The service was buggy, where uploading to the portfolio meant you can no longer edit that photo or share it with the 500px community. This was fixed with the recent update, plus the addition of Flow (a random way to display your photos + favorites), and Store, where you can sell prints.
The new update also has its share of bugs, such as missing EXIF data, endless-loops when editing, or wrong aspect rations in Flow. Their support service seem to be in denial, or trying to sweep it under the carpet. Such handling of user problems isn't very attractive.
I subscribed for 1 year for $50, but I doubt I'll renew if their level of service continues like this.
My portfolio: http://Waleed.500px.com/
The EXIF bug