All good advice. After about the same amount of time, I am seeing things from the other side -- that of the manager / employer. I have had quite a few employees who came to me and sheepishly told me they were accepting another offer. In every case, my response has been "Congratulations!" and it's sincere because these people are also my friends. I want them to win! As their manager, part of my job is to provide an environment where they can grow their skills. If they grow faster than the business grows, economics tells me what to expect.

If you tell your employer you're leaving for more money and they get angry (assuming you didn't just consume a bunch of money in training), that's a sign that you made the right move.