This paper analyzes the impact of residual transmit impairments on the performance of multiuser Multiple-Input Multiple-Output (MIMO) systems. We focus on the uplink with Decision Feedback (DF) non-linear receivers and the downlink with Tomlinson-Harashima non-linear precoders. We show that transmit noise severely affects the performance of both non-linear transmission schemes, specially for the downlink with THP. Nevertheless, this degradation can be significantly alleviated when including the transmit noise into the transceiver design.