Actually, Android is very good for its short amount of time in the market.
OS and Windows have been around for nearly 30 years.
Android? 5 yrs.
iOS was released to the public in June 2007. Android's first beta was released in November 2007.
If you're talking about OS X (which shares the same kernel as iOS) it's only been around since roughly 2000. OS X is completely different than the old Mac OS versions. If you really want to be nerdy and say that OS X is just Unix and it's been around for around 30 years I'd agree.
Windows RT would have been much more interesting it it had been Metro (or whatever they are calling it now) *only*.
As far as the application argument goes, "apps" as we've come to call them represent a new generation of software and I don't think it's necessarily fair to compare them to traditional desktop applications. That goes regardless of what platform you're talking about. When people talk about wanting "apps" they're probably talking about software that works on a tablet that doesn't include things included in the traditional Windows/OS X/Gnome/KDE user interfaces.
And Kaplin, I've never said that tablets will fully replace laptops or desktops for many purposes. For lots of people in a number of situations a tablet of some kind works as well if not better for them than a laptop. It's the whole truck vs. car analogy. Trucks and full computers are good for heavy tasks. Cars and tablets are better for other things.
Put a different way, if all I'm going to do when I'm away from the office is reading or writing then a tablet works just fine for me. If I need to work on a spreadsheet or crunch some real data then I need at least a laptop if not something bigger. That means that my iPad has replaced a laptop for me when I'm going on weekend trips but it sure as hell hasn't replaced my Precision M4500 laptop or T3500 workstation for other work.