Mid 2010 i7 Macbook Pro 6,2 stuck at Apple logo on boot
The fact that it boots perfectly fine in safe mode points to a problem with your graphics card. Safe mode disables all hardware drivers besides those absolutely essential to the operation of your system, and that includes hardware graphics rendering. The reason your graphics are so choppy in safe mode is because everything is rendered in software (i.e. by your CPU) rather than in hardware (by your GPU). I doubt it's a hard drive issue simply because you have no problem installing ML or booting up. 

The good news? Since your repair was around a year ago, you might be able to convince the Apple Store people (talk to the manager) to replace your logic board for free.