Testability is likely to degrade with a more highly coupled system of objects. Object interaction complexity associated with coupling can lead to increased error generation during development. Low cohesion adds complexity which can translate into a reduction in application reliability. Objects which are less dependent on other objects for data are likely to be more reusable. If objects are actually being designed to be reusable beyond a single application, then the effects should appear in object library usage statistics.
More complex methods are likely to be more difficult to maintain.
Greater method complexity is likely to lead to a lower degree of overall application comprehensibility. Greater method complexity is likely to adversely affect application reliability. More complex methods are likely to be more difficult to test. One of the goals of object-oriented design is finer granularity. Therefore, each object's behavior should be more easily understood and analyzed.