I have found the GPS in my Ipad2 to be so unreliable it is all but useless
The quality must vary quite a bit because mine (iPad2) is sufficiently reliable to be quite useful, in 152/172/PA28 and Landy all with metal roofs. However it's not faultless, any more than the 430 is, and will occasionally show the little plane pointing the wrong way or stationary. Sometimes this condition lasts for a minute or two.
I think this is a good thing since you do need to avoid the mentality of trusting one piece of kit to the detriment of the rest. Frankly, if iPad/SD was 100% reliable then you would not bother switching on the rest of the navaids, let alone carrying a map.
I'd suggest an ipad with a really poor gps might justify a visit to the apple store.