By the same argument, Macs should be worth about half as much as comparable Windows systems. (Software quality is comparable, and if you want quantity of software, Windows is way ahead.)
Yes, kind of. Quantity and quality of apps is very important. In the case of windows/mac not so much, because most people will find what they need on either platform. There's still a lot of more specialist stuff people need windows for though - that's why it's more advisable to go with windows for say astronomy. At work I use a mac with vmware for the windows software I need, at home I don't need windows at all.
On the tablets the software library is much smaller though, so here iOS has a big advantage. For astronomy, it's very hard to recommend android over iOS, because so many high quality astronomy apps are only found on ios. Between android and playbook or touchpad, it's easy to recommend android, because the others are even worse.
Really though you can never say iOS is better than android in general, because they both do certain things better than others. Astronomy apps? iOS. Customisability? Android. Games? iOS. External hardware? Android. And so on.
You do realize that the HP Touchpad runs WebOS, not Android? And the Touchpad hardware is made by HP, which doesn't make any Android tablets?
I suggest you try a Samsung Galaxy Tab 10.1 before jumping to conclusions.
Yes, I absolutely realise that (I have a touchpad, and might use it for android dev at some point if android is ported to it). And I didn't make any conclusions on android at all there - I concluded that the touchpad was worth much less than the iPad based on quality. I own and use both, and the touchpad is terribly slow, and generally of lower quality.
On the galaxy tab, I don't know, I've only tried one out fairly briefly in a shop. Android varies wildly though, you get some REALLY nasty tablets at the low end, and good ones like the galaxy tab at the high end.
Related rumour: I've just seen somebody mention on twitter that amazon is in talks with HP over buying palm! That would be a pretty amazing twist, if it's true, but the day after they release an android-based tablet? Maybe if they're pushing it as a media playback device rather than an app running device, but it wouldn't fit in with the amazon app store at all. Unless they're thinking webOS running android apps? I think it's likely bs