I can comment here as I have been having the same dilemma for the past 6 months. I have a X1 Carbon sitting here next to me. I was able to special order it from CDW so I received it with the Intel 240GB SSD (full disk encryption), 8 GB RAM, and the Intel 2.0 GHz i7.
As far as the X1 goes, there is no doubt in my mind that this is the best notebook design on the market. I travel extensively throughout the world and I do not have one concern about its durability when traveling through security, using it in the airplane, or even at the local coffee house. The fact that it is made from carbon fiber and passes 8 of the 9 MIL-specs right out of the box makes me comfortable that I can put this laptop through its paces.
However, there are some shortcomings with the X1 that I have found and they are the following:
1. Windows 8 - I do not care what others say about the Metro/Modern UI/UX, it is brutal and does not work for me. I have tried Ubuntu and it works flawlessly on the X1, but I really need to be either in OS X or Windows to get work done for what I do for a living.
2. The screen has acceptable viewing angles, but it is still a TN panel and could be better for how much I paid.
3. Battery is O.K., if I am conservative I can get 4-5 hours.
4. Wifi drops out randomly and I think it may have to do with the carbon fiber design.
5. Would be nice to have Haswell and 2 x USB 3.0 ports.
6. Charging adapter is not as good as the Apple Magsafe idea, and I know this may be a small thing, but when you travel a lot, these little things make a big difference.
7. Fan Noise - this is a big deal and I cannot for the life of me understand while Lenovo cannot create a thermal cooling system similar to Apple. The fan on the X1 full go full speed as soon as I disconnect the power adapter and that is with me just typing in Word. In addition, if I have no applications open and the screen shuts off in power save mode, again the fan will go full speed with no tasks running in the background according to Task Manager.
8. The new trackpad, while larger in size, still does not even come close to the ones on the MacBooks. This really blows my mind, how is it no one has yet put this much effort into the trackpad on the Windows side. You simply cannot touch the trackpad from Apple and it makes a world of difference in the computing experience. Don't even get me started on Windows 8 touch screen enabled laptops... this is an absolute joke and will fail miserably.
Now for the things I like about the X1 Carbon:
1. The best designed laptop, period! It is sleek, black, has the soft-touch matte feeling with carbon fiber design. The X1 feels like it was built to stand the test of time.
2. The keyboard is second to none. If Lenovo put as much effort into their trackpads as they did their keyboards they would have a winning combo on their hands. I can type on this keyboard all day!
3. 1600x900 resolution with MATTE screen makes me happy (really dislike glossy as a personal preference).
4. Lenovo support is usually good once you get to tier 2, but the fact they are in the USA and are generally available to come on-site to make repairs makes me know that I will only be done for a short period of time in case of needed repairs.
5. Charges quickly...
6. Port selection is good - mini display port, secure digital, 2 x USB
7. Track point - it is nice to have both options
8. I like the fact that I can find anything I need on Lenovo's website about the X1, including the service manual. The service manual clearly explains how I can completely disassemble the X1 and contains all the part numbers I would need incase of having to order spare parts and performing the repairs on my own. Try doing that with Apple....
What I Do Not Like about the MBA
1. Keyboard vs X1
2. Screen resolution and this silly glossy overlay
3. Cannot fix or repair myself
4. Aluminum design will scratch easy and bend easily if dropped - don't have much confidence traveling with the MBA
5. No Mil-spec testing
What I Do Like about the MBA
1. OS X
2. Magsafe and Apple battery technology - 10 hours compared to the X1
3. Trackpad
4. Port selection 2 x 3.0 USB, Secure digital, thunderbolt/display port
In the end I am sure I missed a few points but I hope that gives you some insight. Now, here is where I am today... I just ordered a MacBook Air 2013 with i7, 8GB RAM, 256GB SSD. I received both Samsung panel and SSD, so that satisfies me. The reason I decided to order the MBA is simple... I really have a great disdain for Windows 8!!! I do not know what Microsoft were thinking, but they better get their act together. I have nothing against Apple or Lenovo, I like both companies.
It is Microsoft that is really causing me to make this decision, and it is an easy one. Apple and their ecosystem really just do work together. In addition, a lot of great applications have been created for Apple over the last few years, but I fear some of the Indie apps I use could just disappear because they do not have large financial backing. I have had this happen to me on more than one occasion with productivity software where I get a system in place and then the developer stops developing the software. The same with Apple and their OS. When they went from Snow Leopard to Lion is when I went back to Windows 7 and now with Windows 8 I am coming back to OS X. I am excitited to see what Ive has in store for the future of OS X - I just wish they would allow me to install Snow Leopard on my 2013 MBA. However, I cannot explain to you how easy it is to just get work done with a Mac and OS X. If I could I would rather have OS X on the X1 Carbon.
So right now I have 2 weeks to return the MBA and for me it simply comes down to deciding what is more important... A well constructed laptop like the X1 Carbon vs OS X. I know that sounds silly, but for the travel I do the MBA cannot hold a candle to the X1 Carbon and if anything goes wrong I have to deal with going to the so called Apple Geniuses which I do not really enjoy plus its a one hour drive and I have to go into the shopping mall of all places.
Disclaimer:
-Sorry for the poorly constructed sentences and grammar
-I have been using Apple and Microsoft products for my entire life so I am not biased either way