Cellular networks today are interference-limited and will only become increasingly so in the future, due to the many users that need to share the spectrum to achieve high-rate multimedia communication. Despite the enormous amount of academic and industrial research in the past 20 years on interference-aware receivers and the large performance improvements promised by these multi-user techniques, today's receivers still generally treat interference as background noise. In this article we enumerate the reasons for this widespread scepticism, and discuss how current and future trends will increase the need for and viability of multi-user receivers for both the uplink, where many asynchronous users will be simultaneously detected, and the downlink, where users will be scheduled and largely orthogonalized, but the mobile handset will still need to cope with a few dominant interfering base stations. New results for interference cancelling receivers that use conventional front-ends are shown to alleviate many of the shortcomings of prior techniques, particularly for the challenging uplink. This article gives an overview of key recent research breakthroughs on interference cancellation and highlights system-level considerations for future multi-user receivers.