Just because you have not experienced any problems, that does not mean there are none.
I have experienced problems and, as a programmer, have had to implement some pretty imaginative fixes. For instance, the dimensions of fixed-size windows are reported incorrectly if aero is enabled so for purposes of accurate positioning, I had to make all such windows resizable and then override message handlers so that they couldn't be resized. On a scale of 1 to 10, how poor was MS testing of Vista would you say? It took me only a few minutes to discover that bug but a lot longer to fully implement the workaround.