I've got 3 instances mining, on one of them its working great. On the other 2 though every block I mine is not accepted/unconfirmed. All 3 are up to date on the blockchain and I've tried restarting the wallet, anyone got an idea why this is happening?
I would say luck.
I did mine at home and at work with 2 different wallets. I did get a block in the first 15 minutes on both PC's.
But after those, I did get only 1 confirmed block in a 6+hours combined. Maybe it's just suspicion but it might favor new users, probably to give them motivation.