btip, you have to pay taxes on it because in your state you did not pay tax on your entire adjusted gross income. You only paid on what you made after paying federal taxes. Since you will be paying less in taxes to the fed, that portion will be taxed now by your state. Most states, mine included, tax your entire adjusted gross income after deductions. FWIW, my state taxes the shit out of me.
Most all of us will be taxed less this year and the $300-600 is an advance on this. It is not free money falling out of the fucking sky. Some sound like a bunch of welfare bitches.
The $300-600 advance is meant to give the economy a little push. If you live on this planet you ought to realize we can use it.
Every year or 2 there will be further tax reductions and benefits. In ten years (yes that's 10, for all of you immediate gratification types) there will be substantial reductions. I know I can use it. Uncle Sam currently ends up with more than half of what my wife and I earn.
Finally, I am also tired of hearing the "what, only $300" types whine about how their 300 doesn't amount to enough to help the economy. Consider this, your 300-600 gets spent, goes into someone elses pocket who spends it, etc. etc, etc. This becomes a huge addition to local state and federal economies.