Interesting question - I just had the same conundrum myself and was originally looking at 15 inch laptops.. but then I found out about the m6600 and found a great deal on one on ebay. You dell haters obviously haven't tried this machine yourselves.. it's amazing. Warning though - it's huge. Quite a bit bigger than the macbook pro 17 inch.. in all three dimensions. HOWEVER.. it has an amazing cooling system and a great keyboard. See here for a great explanation of how awesome this machine is: http://forum.notebookreview.com/dell-latitude-vostro-precision/597919-m6600-owners-review-warning-large-pics-personal-opinions.html
I'm running ubuntu 11.10 on it at the moment and it's working great so far. I'm just trying to figure out whether I want the AMD drivers for the firepro graphics card.. so far the open source ones are working fine with both unity and gnome shell though, so this isn't really a problem as much as it's a choice. I'd totally recommend the m6600 if 'extreme portability' isn't one of your main concerns.
Let me qualify this post a bit - Starting in 2006 I used a 15" HP nc8430 with ubuntu/windows dual boot, for 4 years solid with a few niggling complaints here and there (mostly software related). Overall it was a fantastic machine. I even recently upgraded to ubuntu 11.10 on it, in fact and it's still working great. At work, I used ubuntu, but while on the go and while at home I used windows, mainly for the better battery life and ability to play some games.
Then I switched jobs in mid 2010 and had the choice of a thinkpad or a macbook pro 15". I tried the thinkpad at first, but it had a horrible screen (way too dim) and terrible battery life (It might've been a dud). I decided to try the macbook since I knew it was more expensive than I'd ever purchase on my own, but regardless of everything I tried, I couldn't stand OSX. In the end, I decided that my beef with it was the lack of customization abilities.. if you don't want to work on things 'the apple way', you're totally out of luck. So, I tried putting ubuntu 11.04 on it. Wow.. what a mistake. There is nothing more frustrating than trying to run ubuntu on a macbook. No right-click-drag at all, and right click on its own is difficult. No middle click. Spotty wireless. Horrendous battery life (would get 8 hours in OSX, barely over 1 hour in ubuntu). After a few days of looking for solutions and finding nothing but other complaints online, I installed windows 7 on it. Turns out the macbook pros are some of the best windows laptops you can buy. Battery life was excellent (on par with OSX), the clickpad is great, (except you still can't really right-click-drag easily), and all hardware works fine given the bootcamp driver package. Overall, this was a great solution for me as it allowed me to game some while on the train and get work done in an office environment that used outlook and MS Office heavily.
After a little more than a year with the macbook pro, I'm at yet another job now.. and there were no 'company laptops' I had to choose from this time, so I was able to pick anything I wanted. I shopped around for a VERY long time, and had a budget of around $1,500. My main shopping points were power, great screen with as high of a resolution as possible, good ubuntu compatibility and decent battery life. Naturally portability was a deciding factor, but I was willing to give it up for the right combinations of features and price. I chose the Dell M6600 (very surprised to choose a dell, as I had the previous negative perceptions of them that many people do), mainly because of the convincing personal reviews of the machine and the fact that the specific deal I found on one offered far more computing power and expandability options than anything else in its price range.
I put two SSDs in it, one mSATA 128gb and one 2.5" 40GB, and it holds both of these along with the original 750GB 7,200 drive and the slot-loading dvd burner. Ubuntu is on the 40gb SSD, windows 7 is on the mSATA SSD, and the 750gb drive holds my media. Ubuntu is faster than a bat out of hell (boots in about 10 seconds, applications load instantaneously) and the open source drivers work great with the firepro m8900. Battery life could be better under ubuntu, (I can get about 1:20) but I'm confident this will be improve over time. In windows battery life is a bit better, offering up to 3 hours with light usage or a little over 1 hour while gaming.
The main things I'm really liking about this laptop after a few weeks of heavy use are:
- The screen - matte finish, 17" of 1080p goodness, led-backlit, very bright if you want it to be, excellent colors
- Keyboard - great feel and action.. good layout, dedicated pgup,pgdn keys next to arrows.
- Cooling system - even while gaming the fans do a good job of keeping the system cool.. without getting noisy. In fact, the macbook pro 15" got louder and hotter under the heavy load of gaming.
- Build quality and looks - total 'sleeper' machine. It couldn't look more utilitarian, but everything is clean, polished, and put together very well. Working inside the machine is a joy, and if you like the 'form follows function' look of thinkpads but can't stand the 80's color scheme, this might be the line of laptops for you.