I don't ignore their tests. But, I would sure supplement them using my own eyes as a guide.
For example, if you look at Sensor numbers, Signal to Noise Ratio comparisons and more between the Nikon D300 and D90, you'd assume that the D90 has much better image quality.
But, if you look at the photos, you may come to a totally different conclusion. For example, if you look at the D90 review at dpreview.com, they have some comparisons between these cameras at both the raw and jpeg level. They indicated that no amount of reshooting could get the D90 to match the D300's output (and they made similar comments about them for both raw and jpeg images).
It's also very difficult to judge the quality of things like noise patterns by looking at their graphs. Originally, they had .pdf files online for cameras tested that allowed you to see the patches they were measuring to get a better idea of how cameras compared. But, AFAIK, they don't let you see that anymore. Instead, you're stuck looking at numbers and graphs to try and tell how image quality compares (which IMO, by themselves, can be very misleading).