I used before bountyhive and bountyplatform in addition with this forum to participate in some bounty campaigns. But actually, I prefer to focus with the Bitcointalk forum, because the number of bounties is much higher and you have the chance to select the best and most profitable ones.
Are those platforms really automated? I see that there are many bounties which uses those bounty. I'm only familiar with bountyhive because it has been promoted before with a bitcoin paying campaign. I guess that's the least idea that I know with that platform. I've joined a bounty before and I prefer to join a campaign that has escrow funds whether in altcoin and has a reliable manager. My current bounty paid me upfront so that's a case to case basis.