It's tough luck for those lured over. You should have stayed at 3.0.1, it's been a well known fact tethering would be broken in 3.1.
I havent changed to 3.1 for this reason..I was just wanting to know when it might be safe to do so as there are improvements in 3.1 that we might want to make use of (podcasts sorted correctly, augmented reality apps)