I don't know why anyone is surprised. Maintaining lower tax rates, instead of raising them, has encouraged people to engage in business activities that produce tax revenue instead of working to avoid it. You never hear this news when taxes fail to go up. Partially government accounting is to blame. When tax cuts are seen as expenditures and increased revenues are seen as a means to spend more, then an increase in revenue due to lower tax cuts must be brushed under the rug.
In other news Private payrolls continue to expand, not surprising now that unemployment benefits are allowed to wind down. Also not surprising is that more people are re-entering the work force, thereby increasing the official unemployment rate. Unofficially and more accurately, unemployment is still somewhere closer to 15% than the 9% currently reported. The discrepancy comes from the fact that the "official" number doesn't factor in people who have stopped looking, taken early retirement, or have taken low paying jobs now that unemployment has run out.
Hopefully, this increased revenue gets used to reduce our deficits and pay down debt rather than provide an incentive for our government to go on another debt fueled binge.