Solved: If the market is growing by 15%, and your sales are growing by 12%, is that a good thing?

No, it is not good and it is the time for the organization to look at the strategies and realign it according to the new market conditions.
In the given scenario, market growth rate is beating the sales growth rate of the particular company. Hence, it will cause the market share of the company to shrink over a period of time, though the absolute size of the sales revenue will increase. As a result, market share of the competitors will increase. Hence, the market power of the company in discussion, will come down and it is not good for the company.