I like the community Beta, except for the upvote/downvote system.

And I see no other valid reason against it.
It's organized, nice and tidy. Things are actually seen by rioters. Most people I've been around are nice and give valid feedback.
-> It's just a great place to throw out your ideas :D

The normal forums are so massive and drowning, and everything is so ... anonymous. It's really not that nice (<- personal opinion <- can't stress this enough :/)
So the people who like the new community should just hang around in that community and the people who like the original forums should go there. You aren't forced to stay here, with the exception that some rioters prefer the community as well, and if they do decide to make their threads here, then just hang around for as long as the thread is active ! :D
But it works the other way around as well, sometimes on RoG I see the chat-logs of rioters asking for feedback on champions I would have loved to have given feedback on, but whoops! You snooze, you lose. :(
I'm staying in the new community so I also have to live with it's disadvantages (like annoying little kiddies, that downvote your threads after you reported them for spamming -_-).

Now, if they decide to delete the old forums, or somehow force you to stay here. Then, by all means, go ahead and rage about.(Sorry, didn't mean it like that)
But maybe there's just something I missed, did Riot do anything terrible ... again ? ^_^