The new iPad3 is much the same so far as the GPS is concerned as long as you select the with 3G model. I find it is pretty reliable but if I intended to depend on the iPad then I would probably buy one of the dedicated receivers that are available for the iPad.
For avaition use (but I have to say I rarely use mine for that purpose and it was not the reason I use an iPad) it is a reasonable, if not great piece of kit. Personally the dedicated receivers from the likes of Garmins have the edge in my opinion for readability in bright light and reliability but the size of the screen on the iPad is superb feature.
If I wanted a moving map GPS solely for flying I still wouldnt buy an iPad but its a close call.