Couple things that I think mitigate the highlighted concerns above. First, if an I4 makes more HP and torque than our 3.5 V6 and weighs less it should be all good. Second, the GXP engine is shared amongst the Solstice, Sky, HHR, and Cobalt so there should be plenty of engines out there. I haven't priced them yet though.
I saw that too, and here's an interesting note. Although the AR-5 is only rated at 260 lb-ft of torque, if you have a certified GM dealership install this turbo upgrade it does not void your factory powertrain warranty. So does that mean the transmission will handle that much more power? Or does the GM warranty not cover the clutch or other parts? In either case GM must believe it will be reliable enough not to piss off upgrade customers.