AndandTech has thoroughly reviewed the new Penryn-based MacBooks and MacBook Pros and concludes: "The biggest improvement by far comes in the battery life department. Just as we had seen earlier, you can expect these new models to outlast their predecessors by a good 7 - 15%. The performance side of things is more of a mixed bag. There are some situations where Penryn is clearly faster than Merom while others show the two with equal performance. It's for this reason that we say the biggest improvement lies in battery life, not performance." This puts to rest any uncertainty over the new laptops' battery life.