Selectively buying Apple's portable devices

OK. In this year, Mac OS X 10.7 Lion is supposed to be announced.
The 10.7 Lion is said to have a capability to use it like iPad.
As you can see from Mac App Store, I expect that equivalent Mac apps to iPad apps are to be announced for at least popular apps. (e.g. Angry Birds )
Then using Lion on MacBook Air will be almost like using iPad.

At this point, it becomes interesting what devices to buy?
As an end-user, you can buy iPad as a street-device. You would usually surf web, check email, and so on. It is perfect. Although iPad is thought to be a "consumption"-centric device, but even Apple is trying "generic"-device concept with Pages, Keynotes, and iMovie on iDevices. So, I believe iPad will have information-producer apps, if there is a market and once they determine that sales of iPad doesn't hurt that of Mac.

However, as a programmer/developer we are in weird situation.
You will take your MacBooks/Pro with you almost always. They are fully capable devices. They are not only for consuming information. Then why are you going to take another device which is less capable with you? If the iPad is a target machine for your development, you have a good excuse. However, generally you will not want.
You can argue that iPad is easier to read eBooks on it and for casual browsing, iPad is more comfortable. However, why you need to spend more for that unnecessary luxury?

iPad is a perfect in-flight device. Recently I visited Korea. I used my MacBook on a tray popped out from a seat in front of me. Then the guy who sat in front of me suddenly pulled his seat back. My MacBook was almost crushed if I didn't move my MackBook quickly. Also, because of the angle between a keyboard and an LCD screen, it is impossible to keep proper distance from its screen and my eyes.
So, if you are a frequent flyer, taking an iPad with you has a good excuse.

However, generally I think it is a waste of money.
Especially if you buy the MacBook Air, carrying iPad to use it can't justify itself.
iPod Touch/iPhone as a true mobile device, and a lightweight notebook computer as a device you are to use while sitting on a chair is the best scenario in my opinion.

However, what if you want to develop for iPad also?
In that situation, buying an iPad is reasonable. Instead it is better to give up iPod Touch/iPhone if you are not rich. Why? Deploying and testing on iPad for iPhone/iPod Touch is possible. So, it can be a target for apps for all iDevices.

Recently, Verizon announced iPhone 4 on their network. Things became complicated.
Buying iPhone 4 to reduce number of my portable devices looks reasonable but it doesn't cover iPad.
I don't want to pay the data fee whether I use all the allowed amount of data or not.
So, probably buying iPad is reasonable at this point.

If you add a desktop machine to this scenario, things becomes more complex.
With similar price level, MacBooks are still more expensive than desktop Macs.
You can buy a lot more powerful iMacs for the price of MacBook Pro 13".

What do you think about it?
Are you rich enough to buy all Apple's gadget without worrying unnecessary overlapped spending of you money? If you buy all of the portable gadget and carry them, you violate the idea of portable devices anyway. ( Portable and light devices for ease of use while in moving. If you add up the whole weight, they are heavy. )