When it comes to laptops I'm all about thin and light. I've got a Portege R600 and am very happy with it.
I mostly use MS Office apps mixed with a lot of browser-based work so my power demands are low, but I need at least a solid 4 hours of battery life. No need for power graphics or CPU for that matter. I prefer a small screen to keep the mobile footprint minimal, but the 12" of the R600 feels a little cramped when I've got a lot of apps running (lots of Alt-tab'ing) so I do hook up an external display when I'm at my desk.
Can't have too much storage, can we? I'm getting by fine with the stock 128GB in this unit but I keep almost all of my media files on a USB drive that gets backed up to others on a regular basis. My music is available to me all the time (thanks to iTunes Match/iCloud) and I keep a few personal favorite photos on Dropbox. But I generally don't have access to my videos when I'm away from home. That's fine with me.
My next laptop purchase will probably be an ultrabook model but I'm not really planning to be in the market for at least another year so haven't done any serious research. If anyone reading this is using a Toshiba Z830, how about a brief review? Do you miss the optical drive? (I can't remember the last time I used mine.)
In recent years, it's been about chipsets. I always go for Intel with my personal computers, and the chipset tells me what processors and RAM are available to upgrade down the road. I always go for keyboards with number pads, and the bigger screens. I like a nice big display for surfing and watching movies.
Oh... and recently I have been upgrading all of my computers to SSD drives. I put one in my L350 and loved the difference. I ended up swapping one into all of my personal computers. Again, I prefer Intel SSD drives... they are QUICK!