AnandTech tested performance, see
Apple's iPad A4 SoC: Faster than the Nexus One's Snapdragon?
I would not describe these tests as comprehensive, but the iPad seems to be getting at least the 10:6 speedup over the iPhone 3GS you might except just from the clock speed bump. I think this means that there are other tweaks in the A4, or in Apple's software, that give a little extra performance boost but that is all.
I agree that this is perfectly ok performance wise, but it does mean that Android tablets using other ARM chips could be significantly faster. At least if the manufacturers of said chips are to be believed. The AnandTech results indicate that Android on a 1 GHz SnapDragon is slower than the iPad, but a tablet can potentially use higher clock speeds than a phone and can probably benefit from dual cpus.
AnandTech also has an interesting discussion of ARM processors in its (very comprehensive) Nexus One Review, see
Enter the Snapdragon.