Before I purchase, please tell me that you only have to buy the iOS app once and it will work on the iPad (full size) and the iPhone.
The iPhone app will happily run full-screen on the iPad using the x2 option.
The iPad app uses a different streaming technique to take advantage of the new hardware built into the Pro-HD and Solo, supposedly giving a superior performance, and it has a better virtual remote setup to take advantage of the larger screen. Downside is that it won't work with earlier Slingbox models.
They are basically 2 completely different programs that just happen to share the same name, so as far as I am concerned charging separately for them is totally valid.
So your best bet is just buy the iPhone app.
I think it's kind of unfair that they make you buy it for both devices at such a high price. Especially since they block you from viewing with a web browser on the iPad or iPhone.
My experience using the iPad app with my DirecTV Genie is less than stellar. It's sluggish to say the least. It works so much better in a browser on my computer so I don't think the problem is my Slingbox 350 or the Genie.