Since its 2015 revision, IEEE802.15.4 now supports the OFDM physical layer at 2.4 GHz, on top of the popular O-QPSK modulation. Chips capable of both O-QPSK and OFDM are currently available. The question now is whether OFDM is relevant for low-power wireless mesh networking; given its prevalence in 4G cellular, it could be a game-changer. We start by collecting a comprehensive connectivity dataset, 141,587,000 data points, continuously over 21 days. We then show, in an entirely counter-intuitive manner, that OFDM alone is not enough to cope with external interference and multi-path fading, and we recommend combining OFDM with channel hopping at the link layer. In the presence of WiFi interference, we further recommend using OFDM option 1 MCS3, a fast 800 kbps mode, which does not use frequency repetition, even though the latter is meant to increase frequency diversity.