I know I'm going to get hit hard for this, but I prefer a Mac. The laptop I have now was not one by choice (neither was the previous one). This one is an HP dv6000 base-line model (thanks insurance company 😛) that barely runs Vista....
I used to have Apache, PHP, MySQL, Postgre, and PERL running on here, but after the memory eat killed me, I took it off. I also tried the "prepackaged" deals and they weren't any better (even though I could turn them on and off as needed).
The one thing about a mac that I love is the fact that it runs cooler than most Laptops and typically the OS seems faster. Not to mention, I love the interface. I've only used macs for like 10% of my life (about 2% really developing things) and that was back when mac had the old colored CRT iMacs.
I don't develop on the laptop a lot. I actually am working in my free-time (as skimpy as it is) to move all my web stuff to my new p4 box running CentOS 5. I've got it set up to be in the DMZ of my router so I can access it via IP from anywhere with my laptop and do work. So when I need to work, I FTP in, grab the files, work, upload the files again, and I can test. The only real "strain" on the system is the IDE (NuSphere or Zend, depends on my mood) and browser running concurrently.
Ultimately when I look at laptop specs, I mainly look at how fast of a CPU I can get without increasing the heat produced by it. So a jump from 2.1 GHz mobile processor to a 3.0 GHz processor for a desktop (in a laptop) will show a huge jump in heat. I made this mistake with my first laptop (although boy was it FAST!!). I then look at things like battery life and power consumption. Can I leave my laptop unplugged for long trips and not worry about it shutting down or not hibernating. Then I usually start with the Recommended memory requirements of the OS (Vista is like 1 Gig), add the memory requirements of my IDE (probably like 4 Megs or less) and double that. So in my laptop right now there's 1 GB of ram (remember, I didn't get a choice). My Desktop has 4 and that runs my dev software a lot smoother. I'd rather have an extra gig in the laptop so it can speed things up a bit. After memory, that's when I look a price. Typically, I can deal with a less than 80 gig hard-drive in my laptop. What I'm storing on here is so short-term (because of things like theft and how I use it) and because I store everything on my desktop, I typically save a few bucks on the HDD and put it in the memory and CPU. Granted, my systems may cost a bit more (my first laptop was almost $3,000.00), but they zip any program I throw at them.
You just have to figure out what's good for you. Walk through BestBuy or Circuitcity or whatever computer store near you and play with a few of their "floor models". Get a feel of "what's right" for you.
A hospital in Baltimore uses those. Their ER is nothing but those flimsy keyboards. I guess they deter BBP or don't hold stuff in like regular keyboards. Either that, or they're easier to clean 🙂 But they're pretty neat. They take a while to get used to as the keys aren't as responsive as a regular keyboard. And sometimes you have to adjust where your finger strikes the key, otherwise the strike won't register.