What is micro-oxygenation. Is it good?
The first part of your question is easy, the second a matter of opinion.
Perhaps you heard about the technology from Mondovino, a documentary that left a big impression on the wine world. Micro-oxygenation was cast as a force of evil, threatening to suck character and vitality out of the world's most romantic, subtle and varied beverage.
Introduced on a wide scale in the 1990s, it involves percolating fine streams of oxygen through a vat of liquid in a tightly controlled manner. Too much oxygen bruises and ultimately spoils wine; too little can lead to problems of its own, such as muted aromas and skunky flavours. When added in small doses during fermentation or aging, oxygen softens astringent tannins (essentially by creating longer-chain molecules), and improves aroma and colour stability.
Winemakers have in fact been accomplishing the same result for centuries with the use of oak barrels, which contain microscopic pores that permit wine to breathe slowly and beneficially. And aging in bottle does much the same thing because cork, too, is porous. Modern micro-oxygenation gets the job done quicker, in a matter of days or weeks (though it doesn't replace oak aging, which imparts flavours and complexity of its own).
Thanks to the ingenious technique, many young wines taste smoother at an earlier stage, reducing the need for long-term cellaring to soften tannins in, say, an old-school cabernet sauvignon or merlot.
Is it a good thing? I suppose there's a rough car analogy. Yes if you're the type of person who likes automatic transmissions; not so much if you prefer to drive stick.