If that's what you mean, no laptop is going to be acceptable. Laptop keyboards are crap. Laptop ergonomics are crap. Laptop expandability is crap.
If the question is, "does Ruby run on 2.13GHz dual core machines", the answer is yes.
I like to work from not-my-desk once in a while, so I have a small netbook for that. But honestly, it's so much nicer to work at a properly ergonomic workspace that I rarely do this -- only for hackathons and the like. If I am by myself, I am in front of a proper workstation.
(I also don't like the "well, just ssh from your laptop to a server" approach that others are mentioning. I can feel the latency. If I run Emacs over ssh or X to another machine, I notice the key lag. If I edit files on a remote file system, I feel the latency for operations like "git status" and even saving. Perhaps I am just very picky.)
Well, I tried the 11.6" in the Apple Store today. The keyboard is awesome. It is a full sized keyboard. There is nothing 'laptop' about it. So it is exactly what you are used to if you have been using the recent wireless keyboard.
They're what I'm comfortable with and that makes them good.
PS: I didn't down arrow you. What's with all the Redditesque down voting lately?
Seriously though, I was a big Model M fan for a while. Then I tried something newer, and could never go back.
Also, the new keyboards are less likely to cause your desk to collapse ;)
That being said, the ergonomics of using a laptop-style keyboard is usually much better when it is external than when it is connected to a computer. The thinness of the Air might change this though, haven't tried it yet.
Which model, specifically?
I have a coworker whose right pinky finger starts hurting about an hour into using a keyboard. He replaced his no-name rubber dome keyboard with a Cherry Brown-based Filco, and the problem was solved. The advantage a mechanical keyboard offers over the standard rubber-dome keyboard is that you don't have to press the key to the bottom of it's travel to make it register. This limits the force that your finger is required to transmit to something like 60g, instead of an infinite amount as you press the key against the immobile bottom of the keyboard. Less stress, less pain.
Anyway, if you do get a mechanical keyboard, just make sure to consciously avoid bottoming out for a while. If you pound on it, it will still hurt.
My desktop setup is a matias keyboard.
In my home office I have a MBP w/ a Microsoft Ergonomic Elite Keyboard w/ one 24 inch Cinema display (Apple) and one 19 inch flatscreen. I also use an Intellimouse.
As far as I can tell, that's the best of both worlds. Take the MBP on the road when you need to; stay cozy at home all the rest of the time.
And it costs more than a desktop + netbook combo.
So I'm not concerned if I can't upgrade my hardware down the road. Having everything soldered in place means I get a lighter product with fewer points of failure.
Do hardware parts really fail enough to make it worth eliminating cpu sockets, memory slots, sata, pci express, etc?
Creepage among memory chips is also possible. RAM doesn't sit as snug for the entire life of your computer. It creeps out a little bit over time and allows for dust to prevent conductivity between the chip and the slot. Having everything soldered in place is much better.
The biggest issue, though, is all the added space required for the housing. The slots, connectors, clips, etc make the product bulkier. While that's fine for a desktop it's not ideal for a mobile device.
Not sure that CPU replacement is -that- common an upgrade, even for desktops. Every few years, the latest and greatest CPUs seem to use a new socket anyways.
Only problem is that the 6-core CPUs are $1000 :)
Just because you can doesn't mean you will, in many cases.
This is my basic feeling right now, and I wrote about it in more detail here: http://jseliger.com/2008/12/26/computer-post-desktop-or-lapt... . Notice in particular the apt Lord of the Rings quote at the end.
I think laptops are (somewhat) overrated, though they might not be for you, in the plural sense.