My department has gone through a lot of transitions over the past 5 years, and I've bounced up (with raises) throughout the process. My bosses have been generous, so I've taken what they offered. At the same time, as a regular forum reader, I've read a lot of "don't accept the first offer" type posts. We're going through another re-org, and I'm being offered another promotion. This time, I did some research ahead of time of comparable salaries, and when my boss made his initial offer, my face (unintentionally) showed my lack of enthusiasm. I responded by asking "If I don't accept this new position, can I keep my current one?" and the negotiation began. I ended up with a 10% raise, plus an additional 3% (on this new base) in October. It was painless, too. I think I was always afraid of seeming "ungrateful" if I asked for more money, but my boss didn't react that way at all.
Thanks for the inspiration!