Could you please specify the complaints your are referring to. We released a lot of updates through the last year.
The fact that its really slow and it freezes often. I've seen these complaints from customers in the App Store even from the beginning of this month
Overal working with PS Touch is a lot of fun as you can see here…http://tv.adobe.com/product/adobe-photoshop-touch/
Of course when you work on 12 MP images it's a bit slower then on a 3MP since the OS has to process lots of more pixels.
In addition it depends how many apps you have running on your device. The memory is a very valuable piece on an iPad