But question... Is the double payments thing I've noticed past few days by design, or bug?
Say I earn 100 coins for a block... It will now send me 2 payouts of 100 each (so I get a free 100), and I'll now have a balance of -100 for the account page where all future blocks have to whittle away at that -100 before the next payout can happen.
So on one hand it seems like a way to limit amount of tx's sent, but on the other hand it seems kind of like an unintended bug that can be exploited by pool hoppers for free extra coin.
I can confirm the issue with the following comment: when there was no official Mac wallet 1.2.2 published yet, I built it myself from the source. All seemed to be fine, and I received mined txes from a pool. When I tried to send some amount to an exchange, all my txes were duplicated. Actually, after clicking the send button, they were generated twice in the list of txes, both were successful, and the exchange received double amounts (did not try to send more than I had, though).
After updating to the official Mac 1.2.2 wallet the issue had disappeared. I decided that it was some build issue and did not report it. But after your report it seems there is some issue that needs to be fixed.