Traditional reliability metrics and modeling techniques have been successfully used to analyze the reliability of a system, which typically consists of hardware platforms and software running on top of the hardware platforms. However, there are some new challenges when using these metrics to analyze modern computer networks and telecommunications solutions. This is mainly because the telecommunications solutions have become very flexible and complicated. Vertically, the telecom technologies are advancing in a very fast pace and the current networks are consist of mixed structures with both old and new technologies. Horizontally, the telecom networks carry out diversified applications such as data, voice, and other multimedia services. All of these services involves different service path and network elements in the complicated networks and hence have different reliability levels. This paper discusses some new considerations in reliability evaluations for flexible and complicated services and solutions. It proposes methods to address the new challenges in reliability evaluations. A case study is also included.