Of course not today.
There is no smartphone alternative that runs flash (today!).
But let's skip forward to the end of the year and assume that by then Symbian, Meego, Blackberry, WebOS and Android will have flash support and it may work reasonably well (demovideos i have seen let me believe that).
By then, the iPad may have a major marketshare.
But, by then, a developer can write one application and target 5 major mobile OS and even all major Desktop OS with Adobe Air (keep in mind: Nokia and RIM sell a _lot_ of smartphones). For me, as a developer, i'd like to be able to use Adobes tools to create apps for most mobile phones.
Eventually, in 2011 this will make an impact on sales.
And in the end, there will be a lot of devices with a similar featureset to Apples products, with flash, without vendor lock in, probably even cheaper.
What's SPOD? daringfireball doesn't seem to work today, at least for me.
edit: Ok, google cache brought up the side. So, your single point why a Desktop OS doesn't belong on an iPad, is that it doesn't have a spinning icon indicating app startup?
I wonder how that would work on a device without a mousepoint anyway. So, you are trying to tell me that _every_ iPad application starts instantly? Even bigger games don't have a loading screen? Could it be that iPad apps are rather small? Most apps i run on my Desktop start up instantly, except for bigger tools like an office suite, photoshop, video editors, eclipse, that wouldn't even run on the iPad.