Look at the sales number for the Macbook Air...
So far, the Macbook Air and Apple TV have been profitable if not successful, that's why they are still sold. Notice how they don't get as many updates (especially the Apple TV) than their brethren though.
Such as ? Remember, you're going to have to drag it around in a bag everywhere, not your pocket like a phone. Portability is less than a iPhone, so what would make it so much more compelling ? Other than "it's Apple's new gadget, must have!".
And I have my college degree. Today I use a laptop because I can drag it all over the house and to the garage or to work If I need to show something to a co-worker. And no, a tablet won't be better for any of that since I don't feel comfortable not typing with my two hands and typing on something that's laying flat on its back doesn't appeal to me.
I like you to point us in the direction were we could actually get those numbers for the MBA. Apple doesn't disclose them, so anything you say about the MBA being a failure is pure imagination. Anyway not every product is made to be sold to everybody. There is no "holy grail" in computers or anything for that matter.
Then in the following paragraph you're stating that the MBA has been profitable. Isn't that all that matters? Anyway, the MBA has received as many updates as the MB/MBP since its launch, it uses the latest cpu/chipsets available. That's all that matters.
Well, if the tablet is a thin, light, 10" device, of course it will be less portable than an iPhone/iPod touch, but it will also be more portable than any MB/MBA/MBP, about half the size of a 13" MBx. And it will offer a better viewing experience than the iPhone/iPod touch for things like surfing the web, watching movies or displaying anykind of document.
For the usages vs a regular notebook, we'll have to see what it is capable of. Right now we know nothing, so it is useless to try to compare. And we also don't know how well it will integrate with Mac OS X computers.
All of your usage/concern seems revolving about typing. That's OK. If a notebook is what you need/suits you the best, OK. Apple has plenty of devices you can use (starting at $999). Now some people may not use computers/devices mainly for typing, but for, let's say "consuming" data/media, watching/examining/listening to things. They may not feel that a hardware keyboard is a requirement.
Like you said yourself, the "point and click interface" is what slow us down. Don't you think that multitouch is a mean to accelerate/change the way we "point and click"? I'll give you just an example in my line of work: try freely/manually moving two (or three or more) faders at the same time in the Logic Studio mixer or adjusting the frequency and the level of an EQ at the same time... You can't, because of the "point and click interface", yet it's is something that I can do on a $20 radioshack hardware mixer (or a $100,000 SSL mixing console). Multitouch would allow this kind of interaction and more. More natural interactions. You can do more with 10 fingers than just typing. So maybe this new device from Apple is their second step in the multitouch environment. It could allow not only new/different apps vs the "desktop" ones, but also better ones.
Don't dismiss a product/technology (that isn't released yet) just because you can't see YOURSELF using it (for whatever - good or bad - reason).