The quality difference between even between my X200 and the T420 is substantial, the T420 has thinner plastics, the keyboard isn't as nice (a little too bouncy), and the screen is less than impressive. It's the last of the T-series with the good UltraNav keyboard, so if you're okay with a last-gen laptop, check it out. If you need dedicated graphics, go look at the T420s.
What is impressive about my T420 was price (ebay: $200 for one in B+/A- condition with a core-i5, SSD and the 1600x900 screen), and that it'll take 16GB (~$130) of RAM. My X200 wasn't cutting it as a mobile workstation for Inventor and doing EDA, and I don't have money for anything more expensive, so it'll suffice for the next year or so.
I had the opportunity to use the new X1 Carbon a couple of weeks ago... The keyboard is a step down and the lack of physical trackpoint buttons is TERRIBLE. I wish Lenovo would grow some goddamn balls and stop attempting to copy Apple. Their UltraNav design paradigm was perfectly valid in the market, but they've decided they need to go play me-too even for their core user base.
Sadly, as much as I wish I could switch to a Dell for their screens, their keyboards are so fantastically bad that it's never even occurred to me to look. And the same goes for Macbooks, the trackpad and keyboard just don't work for me. I'm half tempted to pick up an old one and see if I can graft an UltraNav keyboard onto it...
I almost decided to go with a Thinkpad X230 - I have used a X200 running Xubuntu for almost 6 years happily. The X200 just started to fall apart and I was bumping up against the 4GB memory in it frequently enough in the last year to make a change. The X230 would have been way cheaper and supported the 16GB of memory I was after. But work was paying, I try to maximize laptop ROI by not upgrading every year, and the screen on the retina is quite lovely. The trackpad, not as much. I miss the thinkpad red nub.
But, debian Jessie installed very easily and so far, I really like the experience. I'm using XMonad, with very little customization, and in general it seems to be a solid machine. Check back with me in four years. If I'm still using this machine, the switch will have been worth it.
I'm quite sad about how Thinkpads seem to be transitioning from serious, hacker-friendly tools to somewhat generic consumer-grade gear.
I own a 2008 Thinkpad (T400) which still had the metal body, zero flex (in anything, e.g. screen or keyboard), and it is in perfect condition (although it has been replaced due to the hardware being outdated, even with an SSD and 8 GB of RAM added).
My coworker purchased a 2012 Thinkpad T430 which, frankly, wasn't nearly as well built (flex and plastic all over the place). Within a year a piece of plastic side paneling (at the back corner on the right) came completely off.
But even the 2012 Thinkpads weren't THAT bad. Just worse. Since then they've almost turned into consumer laptops in every way, and the recent touchpad silliness just goes to show what idiots they have managing that project.
Thinkpad was a niche product for professionals, field techs, the military, and so on. Their re-aiming it for broad appeal is flawed and dumb.
* The keyboard is fantastic. Feels very natural once you get used to the layout.
* The performance is incredible (3x SSD RAID 0 + 1TB spinner). This has made me much more productive working on a C++ codebase.
* The touchpad FUCKING SUCKS. I think it's a driver issue. I don't say "fucking sucks" lightly. I know how hard it is to hardware and software well but for a laptop as expensive as this one, this really shouldn't be the case. It just randomly decides not to work and it jiggles around a lot. I've had to attach another mouse, it's that bad.
* The sound seems to only come from the right speaker, so I think it's busted.
* The weight is just perfect.
* The drivers come in a CD, but this laptop doesn't have a CD drive...
* The speaker quality is just OK. Nothing amazing.
All in all, if the mouse and sound/speaker issues were not there, I would be incredibly happy with this laptop as a dev machine. As it is though, I will be returning the laptop this weekend.
I previously had an alienware m17x but its power gave out so I decided not to repeat the purchase. The sound on that one though, holy cow, it was amazing and it too was quite fast.
Look into gaming laptops, those are built for performance (if that is what you need).
HTH.
2. HP Elitebook (Despite my feelings about HP the Elitebooks have decent build quality, lower end models however should be avoided)
3. Panasonic Toughbook (More expensive, semi-rugged would probably be the best fit)
I have looked into HP Elitebooks but I have been burned by HP and seen so many others burned by HP that I hesitate to invest in them.
I agree with most of your points about Macbooks, except the VGA one (Mini Displayport to VGA is $15) and the price one (Thinkpads are ONLY about $100~150 cheaper than a comparable Macbook Pro, as long as you compare like-with-like).
The biggest thing Thinkpad has over Macbook is the huge 9 cell extended battery, replaceable batteries, and the "slice" battery. You really can get over a full day of unrestrained usage on a 9 cell Thinkpad with the 4 cell slice (easily 12+ hours) running Windows. And while the MBP's battery life on OS X is impressive, if you run Windows on the thing (either bootcamp OR virtually) you'll cut your battery life down to 2-3 hours.
PS - 3G/4G within a laptop is totally not worth while. Too buggy/problematic. Just buy a "MiFi"-like device (mini standalone 3G/4G to WiFi hotspot with battery e.g. TP-Link M5250). They are inexpensive (MUCH less than paying for the 3G/4G laptop upgrade), can charge over USB (so the laptop's battery can power it), and provide a nice straight forward WiFi signal "anything" can use. They "just work."