there certainly are alot of *opinions* in here on the subject. lol a true marketer will test. first, one must distinguish between a LOGO and a website header. They are not necessarily the same. A header may be 600X200pixels, wherein a logo may be 50X90pixels. Second, you must consider your audience. I am telling you now, that there are people making a LOT of money selling ONE product on a webpage (go see clickbank top sellers), and they do NOT use a graphic logo/website header. But a LIBRARY site, where people do NOT expect to BUY stuff, but are only looking for information, would be better served with a header/logo. Many information sites will be better served with such. Not everybody is building an EBAY or Mcdonalds type corporation, but still make $100,000 or more a year with their network of sites, selling their information products, with NO LOGO and NO header. i think i will leave this thread at that, lol, cause i think since i am contrarian to the multitude of posts here, i am asking for trouble which i do not desire. good luck, and realize that most answers are, 'it depends'.
A good logo is priceless. It symbolizes the emotion of your brand, and is the centerpiece of brand building efforts.
I think a nice looking logo for your site is a good thing. Some times, people remember sites by their logo