The thing I find interesting is that doing the research gives me a new perspective on whether or not I really want to go after that business/model. The SEO search turns up potential competitors, domain squatters, etc. While thinking about different names to lookup and key words to search for, my context changes to a potential customer...

A lot of times it reminds me ("oh yeah... did I talk to real potential customers yet?") and if I didn't, I'm in real trouble of building another tool that no one wants :(