I JB'd my 2nd gen iPod Touch this morning and all was well until I started installing things from Cydia. Now once it resprings it gets stuck in safe mode. I'm having trouble isolating the issues because the first time I tried and had to restore, I had only installed aptbackup to restore my apps. After I restored it, I tried to rebuild my apps from scratch but as soon as I respring it goes into safe mode and whether I respring or reboot it just stays in safe mode. I don't think there's any going back for me, so I'll just have to deal with iOS 4 or attempt downgrade to 3.1.2 and JB that instead. Be careful.