In reply to Reach>Talent: That's all good stuff, but it really depends on the company and it's difficult sometimes to know what they're looking for. I'm a technical recruiter, and feedback from some of my clients has been that some candidates know no more about the company than what I've told them; others (mainly in the defence industry) have very little publicly available information about the work that they do - and so obviously don't expect much knowledge from candidates. It's always better to know too much - no one will every pull you up on it if you're well prepared.
Stalking the interviewers is certainly useful - if you've got something in common it's good to be able to sneakily bring it up. Just don't be too obvious - I once interviewed someone to work for our company who had clearly done loads of digging on all our employees - he just came across as seriously creepy.
As you're going for a technical role, I'd focus on ensuring that your knowledge of your area is top notch and that you are confident on all the areas of the job brief and your CV. In my experience, technical knowledge is where most people fail, and so even if you're confident that you know what you're talking about, I'd still recommend going over your books.
In terms of time spent preparing, we expect our candidates to spend between 8 and 16 hours preparing - sometimes more if it's a second interview and they've been asked to research specific areas.