I'm serious. Every job interview I had where I pretended to be something I wasn't I didn't get.
The job I'm in currently I outright admitted that I disliked a few subjects in school, etc, and actually shown I had a personality. I wouldn't recommend doing this and I class it as a mistake, but I think they appreciate someone who is a little different than every single candidate that has waffled crap that was put on a website somewhere as they probably hear it all day.
It's true, interviewers seem to appreciate forthrightness and enthusiasm more than you would think. Of course, there are some things you probably don't want to tell them, but don't present yourself as a form letter. That makes you look boring.
When I was managing an ice cream shop a few years ago, I found that the more relaxed, lively, and open interviewees made a better impression on me than the subdued ones who were obviously trying hard not to offend me, and they were the ones I generally hired, provided I thought that either one could handle the job (granted working at an ice cream shop doesn't require steep qualifications). Different interviewers have different attitudes, though.
Even if it seems like it doesn't go well, though, you might still be okay. The job I have now (the first "real" job I've had) came out of the worst interview I've ever had.
It's probably a bit late for this, but be careful of what you put on your resume. I had been looking for an entry-level position since college, and I usually interviewed for programming positions. I was taking a networking class at the local tech college, and I put that on my resume under education, because I figured it would show that I was at least keeping busy and trying to improve my skill set while looking for a job, instead of just sitting around. That was a mistake, because every single interviewer I talked to saw that and asked me, usually multiple times, "You know this isn't a networking position, right? Are you sure this is really something you're interested in? Because... this isn't a networking position." Basically, I had to work extra-hard to show that I was interested in the job.
Also, don't be afraid to mention your hobbies on your resume or in the interview if they're potentially relevant to the job. The one thing on my resume that has gotten me more credit and interest with interviewers than any of my training or education, particularly since I didn't have a lot of relevant experience at the time, is the section at the bottom where I mention my Neverwinter Nights script suites and a couple of minor mods and utilities I've written for other games.