In Search Of The Ultimate Mobile Developer Machine

Here we go, please take a ride with me as I search out the ultimate mobile developer machine. Why mobile? Because I hate being tied to a desk. I have desk top machines, but I want something with equal power I can take with me. Here is what I am looking for:

Nothing larger than a 15 inch screen. Yes, 15 inches. Any bigger and it's like lugging around a desktop.
At least 8GB of memory. I would love to have the ability to upgrade to 16GB or even 24GB. Memory is a developers best friend. Next to CPU speed, it's the key to all goodness.
A hard drive fast enough to keep up with the RAM. I really like what is happening in solid state drives (SSD).
A CPU, well, let's look at 4, that will allow me to compile in a split second, let me stream video, rip a DVD, all at the same time.
I would love to have built in 3G connectivity, but the more I think about it, the more I would hate to be tied to a specific carrier. So maybe just a USB card will work.
Ability to read just about any memory card. At least 4 super fast USB ports.
Lightweight. This is a mobile machine, remember?

Honestly, that's about it. Nothing spectacular. The real trick here will be to find one that doesn't weight as much as your Mothers Cadilac, and doesn't cost as much as my last Child.

There are really two flavors, an Apple Mac, like a Mac Book Pro, or a PC which can run Windows or Linux. Since I do a lot of Windows development, Linux probably isn't a viable option. And I don't want to own a MBP just so I can run Windows on it. You think the simple choice is to go with a PC. But there is more too it than that. I have to make some additional choices, to make the right choice.

First, will I choose to stop developing Windows applications. Honestly, that's the key question. I can develop everything but Windows applications on a Mac. I know, I know, running Parallels or VMWare Fusion gives me a Windows machine on the Mac, but I don't want to do that. It doesn't work all that well on my iMac, and I know it doesn't do any better on a MBP.

Throw my hat in a ring, and stay there for a while. Honestly, I'm not sure 100% which ring the hat will fall in today. OK, enough of that, off to find The Ultimate Mobile Developer Machine.

What would you recommend?