I agree with so many things on this thread but not everything.
I fully understand nearfantastica's opening post and completely agree - we should not classify a fragrance as "bad" just because it came from a certain house. However, I think it is justifiable to skip over a scent from a certain house because of past experiences with the house.
Yes, testing fragrance based on house/past experience is kind of biased but as Paul said, there are SO many fragrances and only so much time. Unless we select for certain fragrances to try out, we will spend ALL our time just testing fragrances non-stop. If we stick with what generally works, we will save a lot of time and money in the long run.
There are houses that I no longer seek out. Names that come to mind include Calvin Klein and Hugo Boss. This is because many of their offerings have failed to really impress me. However, there are fragrances they offer that I do enjoy. I love CK Escape in the summer and Obsession in the winter. Hugo Boss Bottled is also great in the winter. However, I can't say the same for their other offerings.
A house which I definitely seek out is Serge Lutens. I like their stuff. I really like their stuff. But that doesn't mean I think every single of their fragrances are masterpieces. Chypre Rouge: I tested it with no preconceptions whatsoever - and hated it. Then I read reviews and saw that I wasn't on my own. YSL is my favorite designer house (followed closely by Chanel). I really like their line for men but I have to admit, the new L'Homme is really not very YSLesque and smells like "just another watered down designer frag!"
What I'm trying to show with these examples is that there's always the possibility of a great fragrance from a house - the only difference is that some houses just offer a higher number of agreeable fragrances than not. IE. 4 out of 5 SL fragrances work for me while only 1/5 CK fragrances work. It makes more sense to stick with a house with offerings that are more likely going to work with you.
I guess THE most important thing, however, is to trust your own nose. If you think it smells good, it does. End of story.