There is a lot that can affect the PEG ratio, regardless of company size, reputation, etc. It depends a lot on industry and company type. For example, utilities companies, will often have limited growth (they've already maxed out their market share) but steady earnings quarter over quarter. Growth factors in quite a bit when valuing a company's future potential but its not always necessary for a company to consistently have solid earnings. A low PEG can be a positive indicator, it could signal a company is undervalued based on its earnings. Since the divisor in the equation is the growth potential, a higher growth coefficient would cause the ratio to be low, so low is/can be good.
*edit* Simple answer: low PEG is good (<1), it means the growth expectation is high compared to the company's PE.