500px is one of the top photo communities today and a place where good photographs are always plenty and eye catching. I am not sure how you can learn photographic techniques from this community, as it is up to the photographers to share their ways and it is not so chat-friendly to discuss on line with the creators. That would require enormous processing strength and bandwidth as there are many registered users. You can actually learn something from their blog, or their new "ISO" site, but generally speaking information is very scarce.
There are many benefits, some more important than others, when you join 500px as a free user. First of all, there is a visit/voting algorithm that is the heart of your "popularity" and 500px. Pulse algorithm was designed to promote daily exposure of new photographs and photographers. There are visits, favorites, likes, affection, pulse and...sales (if you want to deal with that, too). There are daily many photos reaching an affection of over 95% (meaning almost every person that saw them, liked them). Members vote for their favorite photos and in that way the submitter gains "affection" and popularity. I have seen popularity growing very quickly with good photographers, but also with photographers that exchange votes in a silent, almost guilty way in order to be "accepted" and "recognized" in the photographic community.
"Bad" photos sometimes reach the first page of popularity based on exchanging of votes, partnerships and followers that are just friends with the submitters. A good photograph for me is a binary idea, either you like it or not. Trying to explain why you like it, is a common mistake we have all made and will certainly make again, because it is in our nature to examine things once we have the time. A "good" photograph depends on your monitor, on your state of mind and on your willingness to accept the good performance of a rival photographer (oh yes, competing for popularity creates rivalries!) and cast your "like" or favorite. It was not long ago when the "dislike" button was still active making bad people ruin good photographs, and I mean BAD personalities and jealous photographers.
On the other hand, you can't rival how photographers affect their followers, how they make their friends and how votes are raising their popularity by use of shadow profiles and false accounts. You then come to a point where you have to make a choice: to make photographs for an audience, or to make photographs for you (the second choice being the most popular and...unfriendly)! You don't "have" to make friends, you don't "have" to exchange votes, you don't "have" to make yourself appealing and suck up your fellow photographers for votes in this way. This is photography in it's purest form and as a result, popularity stays low and great photographers get lost in the crowd but, my fellow photographer, you can concentrate doing "your thing" and leave everything else out of the equation.
And let's not forget that photography is an "exposure", full time job. Posting a photo exposes it to critiques and also exposes you to good and bad people. There are people trying to learn from your "mastery" and people trying to steal your ideas, get an inspiration, or even steal your photos for their purposes like advertising and news publications (I met almost every one of these types). Don't get me wrong, there's nothing wrong with trying to get inspired, or even copy one's idea (I know what I am talking about!) and color it with your "ways", improve it, make it better or experiment in the process and make more "mistakes". How else can one improve, after all?
But where 500px hits bottom is when you try to search for previous good photos for inspiration. Popularity is a good place to start, but it is based on a 24-hour voting system and there's no way (to my knowledge) to search for good photos posted a month or a year ago. It would be a nice idea (based on a wrong idea, that of popularity voting) for one to be able to search for previous good photos. One could at least find half of the site's "good" photos (remember, based on their "popularity") by using this way, that were posted before.
In conclusion, 500px is worth your daily visits and it is full of inspirational ideas for photographers and visual art lovers. It is the place where you can see astonishing dreams and have a vision on how you can drive your photography craft to evolve. You can make friends or you can simply make vote exchange and be "popular" and even ignore everything and just put your work for the world to see, it's up to you how to use these benefits and improve the way you handle photography and post processing. After all, this is what a good photographer tries to do, improve!