I have to admit I don't know the exact technical details, and my knowledge has simply come from reading this forum, but I do know there are at least 2 different ways of sending/accessing the Sling stream. Earlier systems just used the original method, which relied on full port forwarding, but after a lot of support issues Sling introduced a second method in the later hardware & software which didn't rely 100% on port forwarding. As I understand it, unlike all the other viewing system, the iPad app uses only Method 2 and doesn't support Method 1, basically because of aspects of the iPad hardware. The impact of that is that you cannot use the iPad app to view any Slingbox other than the Solo and the Pro-HD as earlier hardware (Classic, Pro, AV, Tuner..) do not support Method 2. (Note the iPhone app does not suffer this limitation and can be run on the iPad in x2 mode).
I don't know, but I guess you might get better performance using Method 1 with a PC/Laptop than Method 2 with the iPad ?