The Wyner model has been widely used to model and analyze cellular networks due to its simplicity and analytical tractability. The key aspects of this model are fixed user location and deterministic and homogeneous interference intensity. While clearly a significant simplification of a real cellular system, which has random user locations and interference levels that can vary by several orders of magnitude over a cell, a common presumption is that the Wyner model nevertheless captures the essential aspects of cellular interactions. But is this true? In this study of uplink cellular networks, we argue that the Wyner model is only accurate for systems with a sufficient number of simultaneous users. Therefore, it is a reasonable abstraction for CDMA multicell networks but quite inaccurate for those employing TDMA. With single-cell signal processing, the Wyner model fails to capture the fact that intracell TDMA is advantageous over CDMA in terms of ergodic symmetric throughput and that random user locations increase throughput. In the case of multi-cell processing, it is shown that intracell TDMA is suboptimal in terms of ergodic symmetric capacity, which is in sharp contrast to results obtained under the Wyner model wherein intracell TDMA is proved to be optimal.