My 2 cents:
I've been a mac user for as early as I can remember. Started using the Apple II (before the original Macintosh even came out) as a little boy.
For the past 6 years however, I was forced to abandon the Mac and start using Windows based computers for work.
At first it was horrible, felt like going to hell really, but after about 2 years of only using Windows, my fond Mac memories started to fade and Windows XP became "acceptable". I know Windows inside-out now.
In terms of laptops, I have gone from a Dell, to an IBM ThinkPad, to a Lenovo ThinkPad.
Owning a Dell was just about the worst experience ever. Absolutely the worst hardware I ever experienced on a computer (and I've owned quite a few) and pretty much nonexistent customer support (in Europe). At the end I literally had to super glue the case together to keep it from falling apart. Also had the battery go nuts on me (Dell refused to replace it) and my power adapter almost caught fire (Dell: "simple wear and tear").
The IBM experience has been MUCH MUCH better. Hardware quality is very good and no horror stories like I experienced with Dell. However, I'm afraid that the ThinkPad quality is seriously suffering from the Lenovo takeover. If you look at the quality to the T42 to the T43 to the T60, it's painfully obvious that Lenovo has cut costs on the parts. The plastic of the case feels thinner and cheaper. Keyboard seems softer, and more and more hardware problems are appearing. Several of my clients are large companies that have standardized on ThinkPads for many years and they are echoing the exact same thing: Quality under Lenovo has gone down.
So today I ordered my new MacBook Pro 2.4Ghz 15" and I am soooo exited to go back to the Mac. With VMWare for the Mac I now have the ultimate solution for doing my work: Day-to-day email, surfing, productivity on the Mac, software development, testing and demoing with Ubuntu, Debian and WinXP by using VMWare and Bootcamp.
So to make a long story short:
if I HAD to use a PC laptop, I'd probably still get a ThinkPad, but I don;t know for how long. Quality is suffering and this seems to be more of a strategic decision from Lenovo as apposed to temporary QC issues.
...but now that I have a choice, I'm switching back to the Mac:
1. Excellent hardware
2. Even better MacOsX
3. Easy ability to run OsX, Ubuntu and XP at the same time.
Finally:
Someone said earlier that the IBM forums don't have as many complaints about quality issues. I'd like to disagree here. I've been lurking on those forums for some years now and don't see much difference.
Also, I think what it is important to point out is the vastly different nature of ThinkPad users vs Mac users. I'd dare to say that the vast majority of ThinkPad users are corporate users that get a ThinkPad issued to them as part of their job. If somethings wrong, they send it to IT to have it fixed/replaced. IT calls their IBM/Lenovo rep and gets it fixed/replaced very fast.
With Mac users I dare to argue it's the other way around. A large chunk of these users are people that have purchased this computer themselves with their own money. When something goes wrong, they have to solve it by themselves and as a result will generate more postings on these kind of forums.