The first thing we should all understand is that we work at the company's pleasure, so forget all the slogans("Our employees are our most important asset", etc...). Companies do what they need to do to survive or grow and employees should do likewise.
If you like the company, the job, your co-workers and paid competitively you have a great situation. If not, you owe yourself to improve the situation. But understand that "job hopping" is viewed negatively by many employers, so do it to often or risk scaring some prospective employers.
Just remember, it's easier to look for a new job when you have one...;-D