How about a decent desktop computer?
I'll give you the iPhone one. The iPod/iTunes is debatable but you can take that too.
But iPad changed PCs? How?
The iMac is a decent desktop computer. We have people here using them for graphics/after effects/3D, etc. They only use Mac Pros for high end long rendering now because the iMacs are completely capable of doing mid to even high range graphics/motion/3D other then hollywood type stuff. We have editors editing on them in Premiere, FC7 etc. It's is a fully capable machine. Dont fool yourself or let others tell you otherwise. As for gaming...I wouldnt buy it but that is such a small % of the population that Apple will never cater to.
They already announced a new Mac Pro coming in 2013 that is completely redesigned 100%.
In terms of the iPad and PC...are you kidding me? Go look at PC sales since the iPad has come out. It's already been pretty much proven that the iPad has cannibalized Dell and HP sales because most people realize they dont need a desktop..or even a laptop..they never did. The iPad does everything they need.
http://tech.fortune.cnn.com/2012/09/04/charlie-wolf-apples-ipad-is-clearly-cannibalizing-pc-sales/
http://bgr.com/2012/09/04/ipad-cannibalizing-pc-sales-analyst-charlie-wolf/