I have used a T40p since 2005 and a T43p since 2007 and they all still run 100%. Some white spots on the LCDs and the occasional dead pixel but no issues otherwise. I used a T42 for work in 2004-2005 that worked fine as well. In 2008 - 2009 I used a T60. Never any issues. And more recently a T60, W500, T400s and since last week a W520.

Too bad my current employer chose HP as their notebook vendor, my colleagues with a longer tenure all have ThinkPads.

The only issue I ever had was a dead screen after stepping on my W500 getting out of bed: Lenovo fixed it after mail-in, no questions asked.

Obviously buying ThinkPads on clearance with 3 year warranty included is the way to go. In case it breaks down after the 3 years I do not really care but (knock wood) so far smooth sailing.

I've had my T42 since early 2005, when it replaced an A22 that was struck by lightning. Insurance paid the full price . I think these are great machines. The keyboards are far better than anything found on laptops from other brands including Apple. I still use mine as my daily work machine, sitting in a minidock (a real dock, not just a port replicator). I use a Dutch-language keyboard, which is QWERTY with some nice additions for accented characters - real 'dead' keys even without the need for the AltGr key. IBM was almost the only manufacturer at the time who offered a real Dutch version of their laptops; almost anyone in the Netherlands uses standard US keyboards and has to fiddle around with ungainly tricks to get properly accented characters. I already lived in France at the time but had a Dutch IBM dealer ship the machine to my French address... Just the availability of high-quality Dutch keyboards made the choice for me.
After two and a half years the motherboard failed (possibly due to lightning strikes again), and as it came with a three-year guarantee IBM/Lenovo France replaced the mobo of my Dutch-bought T42 really fast and without any issue - next-day courier pickup, and a real French person on the phone to talk to who really knew what the status of my machine was simply because she had eye contact with the technician working on it.
My T42 is now 7 years old, used 7 days a week and it still runs. Last autumn I replaced the fan and the original harddisk, as both gave up almost simultaneously after almost forty thousand running hours (I guess that 40 000 hours must be about the limit for things that rotate very fast - if this was a car it would have run two million kilometers at 50 km/h...). My T42 now has a new 250 GB Western Digital Scorpio PATA hard drive, with a clean full factory-spec system on it thanks to the original recovery discs I made 7 years ago, and with freshly installed favorite applications. It now feels really quick. Note that this machine ran 7 years, 7 days a week without ever once having to reinstall Windows and with few crashes - but it did get a bit sluggish towards the end...
I still like its size and feel - I have come to prefer laptop keyboards to full-sized ones as in these times of graphical interfaces, one uses the mouse a lot. With a full-sized keyboard the numeric pad shoves the mouse more to the right and during long sessions of mouse-intensive work (say, editing photos or designing web pages) this puts more strain on one's neck and shoulder muscles than with a laptop. For that reason I also prefer a laptop that is not wide-screen but 4:3 - meaning I'd go for a high-end T4x or R5x over a T6x/R6x as the latter have wide-screen TFTs. 4:3 with a high resolution also means less vertical scrolling, which is great if you handle long text documents a lot. If you want a reasonably fast 4:3 laptop with a really good keyboard, the T4x/R5x series are obviously the way to go, with the X31/32 as smaller travel companions that will fit into the same docking stations.

You forget that the T60 also comes with a 15" 4:3 standard LCD with IPS screens in SXGA+ or UXGA.
And AFAIK in Europe only there is also an R61 with the same size screen.

Well finally got a T40 (2373-96U) 1.6Ghz, Ati 9000 1400x1050, 1GB RAM, just needed a HD for $33 shipped.

I'm looking at a couple more T61s, with Intel graphics. I don't need all the drama associated with the T40 series combined with their memory, HDD limitations & speed disadvantage WRT T61s.

I never found the T4x issues to really be problematic unless you really were rough or held it in the front making the weight from the back flex the board. I know people who say the T4x's suck just because of what they heard yet I seen so many T4x's still kicking on to this day (like 1 out of 10 T4x's I worked on at my job had graphics issues).

In fact the T40 I own is the best little Pentium M machine I had, cause i used to have a Dell D610 that was "faster" then the T40, but that thing was slower then molasses so I gave it away. I sometimes use it when my z61p is just a bit too huge to lug around (wish I got the T61p). In fact I think the design of the T40 throws my z61p in the water, always seemed to like the T series due to their slimness.

Yes they are dated by todays standards but they still are quite useful machines and I still use mine to this day and had not had one single issue.

BTW, I Never said T40 series sucked, just that i passed them over and went from T30s to T61s (plus some T22s &T23s lying around).

Turns out they have some "issues", some by IBM's design (whitelisting) & some that popped up over the years. Nothing is perfect and there are always tradeoffs. If I ever have the chance to come across a nice T43, I'll probably get one, because they were nice machines, but I'm not looking for one.

Oh I never meant you. I mean people I work with. In fact one guy I work with pretty much says every ThinkPad is nothing but problems, which I know is just a gross generalization to a great brand.

But yes if you ever come across one, get one, it was one 100$ purchase I'm happy with.

I went from a T43 to a X201s then got my hands on the T61 to replace a broken computer. I realized that I really missed SXGA+. With the potential of the T61 (in terms of upgrades and performance and being the last SXGA+) there's really not much reason to look back to the T40 series now unless budget is an issue IMO.

FWIW, my wife uses the T42p and I use a T61. We both travel quite a bit, and these have gone through many airports. They are in use about 6 days a week since they arrived from the factory. The T42 is all original parts and still going strong without any problems that I can recall. The T61 came with a 60 GB drive and Windows XP, I think, then it got a larger hard drive (320 GB) and Win 7 about 2 years ago.
I have not used anything from Lenovo that is newer than the T61, so I am still a little surprised that some people seem very critical of the brand. We still like our Thinkpads better than anything I have seen from other manufacturers (including Apple).
I think we still have some old TPs around here -- we retired them saying we might use them for spare parts. Of course we have not had to use them in that way.