The thing is, it "can" multitask, multitasking has nothing to do with the cpu. The question is whether Apple are allowing more that one app to run at once. I'm not sure that the iPhone does, I seem to think that each apps state is frozen once u take focus off it, but still there are many things running in the background.
Remember, decades ago, Linux on a 286 could multitask, as could AmigaOS on a 25mhz motorola.
It's the kernel more than anything else. Afaik the iPad will have an OSX variant as usual.