My data's several decades old so it may not apply anymore. However, back in the day when I went through my BS in CS, the common understanding was that there were no jobs for an MS (and you were overqualified for BS jobs), and that you only got an MS if you were going for a PHd.
BS = general, MS = becoming specialized, PHd = very specialized.
Anyway, these days, with the economy the way it is, a lot of people are going for more education since it's hard to get jobs on graduation (they're hoping to weather the bad economy). I had posted a link in another thread a while back where they were saying that currently a small number of graduates actually got a job quickly after graduation. I think that's a valid excuse for anyone inquiring, and I think that the businesses will be taking that into account when they're hiring. I'd be leaning toward staying in college right now because of this.
My general thought is that an MS is fairly worthless for the job environment. A BS is all that you need unless you're going for a PHd. There are very few positions for PHd's. BUT, it's a good way to tide you over while waiting for the economy to pick up, without having to pay back some of your student loans.
So, the real questions are:
1) How are your finances? If you don't have the finances to make it through an MS degree, I think that answers that question. Note, if you have student loans, you usually have to start paying back after graduation. If you go to an MS, they'll usually defer till after the MS. So if you don't go for the MS, you have to start paying back now (even with no jobs available).
2) How are your grades? I'm assuming they're good enough to go for an MS, otherwise you wouldn't be asking. However, are they good enough to get into the MS program with all the competition? You wouldn't be the only one trying for it with this economy, and slots are usually limited.
3) Do you like college? If you hate college, it'll be a couple more years of pain and suffering. If you like college, a couple more years of fun. When I went through college, it was ok, if a bit boring. Now that I've been in the job force for years, I miss the good old days of sleeping in, staying out late, wandering around, and generally putzing around having fun with no job related responsibilities...
Oh, and if you ever want to get a Masters, I would go for the Masters right after the BS. I wouldn't wait. You can do it later, but things get complicated in terms of time and money (as well as dated knowledge). You get married, have kids, and next thing you know, you'll be 65... Your greatest commodity after graduation is time.