Driven by the need to improve network capacity, there is a growing interest for dynamically utilizing spectrum over a wide range of frequency bands. The available spectrum is typically divided into multiple channels. Past work on designing protocols for multi-channel wireless networks has assumed that all channels are homogeneous. However, channels that are located in widely separated frequency bands exhibit considerable heterogeneity in transmission ranges, data rates, etc. In this paper, we identify the impact of channel heterogeneity on network performance, and motivate the need to account for channel heterogeneity while designing higher layer protocols. We present some approaches for managing heterogeneity, and propose hiding most of the channel heterogeneity from higher layers by designing suitable channel abstractions.