Future 5G networks will likely include mmWave radio access communication links, because of their potential multi-gigabit-per-second capacity. However, these frequencies are characterized by highly dynamic channel conditions, which lead to wide fluctuations in the received signal quality. This article explains how the end-to-end user experience in mobile mmWave networks could be affected by a suboptimal interaction between the most widely used transport protocol, TCP, and mmWave links. It also provides insights on the throughput-latency tradeoff when Multipath TCP (MP-TCP) is used judiciously across various links, such as Long-Term Evolution (LTE) and mmWave.