Ask HN: Should I take interviews for practice/leverage?

I've been looking for a job. A few companies/recruiters have contacted me asking if would come in for an interview (I didn't apply). I'm reasonably sure that I would not accept an offer from them (due to company size, the company's product/market, and/or the company's brand), even if they gave me one. On the other hand, some engineers I've spoken to have said that their initial judgment of a company was proven wrong or changed when they actually interviewed.

That being said, should I (ethically) take interviews just for 1) practice, 2) leverage with the companies I actually want, and/or 3) the possibility of being pleasantly surprised, or should I just decline and not waste their time?

Back before I became a consultant after about 2-3 years at whatever my current job was I'd start taking a couple interviews every 6 months. This allowed me to gauge the market for what skill sets/tools were being used in my area and also what salaries are offered. I never considered using this information as leverage though, I just left when I got a better or more interesting job offer. Now I consult so I am interviewing every 6-18 months anyways.

Do you currently have a job? You have to usually waste a day traveling or going to their site. Many times interviews are very poorly organized. I think unless you have a definite end goal it is waste of time.