I have a 64-bit Vista computer that generally works really well. It is fast, and it did not cost much. Vista is obviously quite unpopular, but I suspect that most of it comes from being the first widely-adopted 64-bit operating system platform. Even Linux has been quite slow to get a decent implementation (my Linux box is 32-bit on a 64-bit box).
The least reliable program so far has been QuickBooks. I had to upgrade for it to work on Vista, but the new version really does not seem to like 64-bit. Its printer drivers keep getting corrupted. I don't really need to PDF many QB reports, so that was no big deal.
However, enter Photoshop CS3. I generally love it, but then it stopped opening files. It turns out that a corrupted printer driver kills Photoshop. I tracked that down with a 3.5 year-old post. So Adobe never fixed a known bug, and it flared up because Quickbooks did a bad job implementing on a first-attempt operating system.
The solution was to delete the Quickbooks PDF Converter. It will be automatically re-installed, and it will probably be automatically re-corrupted! I had to cancel all documents and run as administrator for the printer to actually disappear.