One of the members of the Writers' Thingie recently finished reading a book (well, actually all members have usually just finished reading something. A particular member just finished a particular book). And one of the criticisms was that the writer seemed to be showing off her research.
Knowing about your topic is great. I took a feature writing course in the Irish Writers' Centre last year, which was great, and is starting again soon. Some of what I learned about the life of a working freelancer has been really useful for my novel. My main character's flatmate, best friend and hetrosexual life partner, Sammi, is a freelance features journalist. This is incredibly useful for the plot, because she has access to information that not everyone knows, she can have free time during the day when the plot demands it, and I can contrast her lifestyle interestingly with Becky, who lives to work.
But there is a fine line. No one is going to read this novel to hear about the life of a freelance journalist, yet if I got it wrong ('Sammi wrote one column a week about shoes and sex and always had money for Manolo Blahnik sushi cupcakes. . .') it would stick out a mile and annoy people. So the research is certainly worth doing. It is important, though, to strike a balance between interesting and authentic detail, and writing a report of your research instead of a novel.