In the 3GPP LTE Release 13, NB-IoT and LTE for Machine-Type Communication (LTE-M) were standardized to provide wide-area connectivity for IoT. The technologies in 3GPP Release 14 evolved beyond the basic functionality specified in Release 13. In 3GPP Release 15 the evolution continues. To optimize the support for infrequent small data packet transmissions, a mechanism for data transmission during the random access procedure is specified for NB-IoT and LTE-M. This mechanism, hereafter referred to as Early Data Transmission (EDT), improves the device battery life and reduces the message latency. This article provides a description of the EDT feature and presents simulated results for the expected battery life and message latency for a set of typical IoT traffic models. For a device in extreme coverage, EDT can enable improved battery life by almost 3 years and reduce message latency by more than 3 seconds compared to the Release 13 performance. Although the absolute gains are highest for devices in challenging radio conditions, significant relative gains are also presented for devices in good coverage.