I have a 2011 GT
w/man trans, and I recently bought a SCT through Lethal Performance with Jon Lund's 93 aggressive cammed tune. If you search this forum, you will find my thread on this subject with input from Jared at Lethal. It was my conversation with him that made me feel good enough to give it a shot.
I haven't got exhaust yet, so the car doesn't sound as good as those on YouTube. Without exhaust, it sounds like it has a miss. Also, with the AC on, the RPM's surge every once in a while to about 1200-1300 RPM. With AC off, it is very steady and will sound great with exhaust. Moreover, I feel like the more exhaust one has, the better the sound will be.
Now for the bad. The tune really drops the RPM's, and when slowing down, you will have to engage your clutch a lot sooner than you are currently use to. I push in at about 1200 RPM because if it drops to 1000, the car surges like crazy. Also, I wasn't prepared for the roughness of the idle, it's just like having cams, and this aspect really surprised me. The car shakes only while idling. Lastly, I was ready to switch back to stock, but have since gotten use to the roughness. The tune is great performance wise, and after you drive it, you will tell it is safe and not hurting the car.
Long story short, I feel Lund's tune is safe, and the car will sound great with exhaust. I just wasn't expecting to have to change my driving habits, but after a few weeks, I am use to it.