Had it manage an Ethernet Phy IC via an MDIO interface, and an FPGA over SPI. The MDIO was bit-banged from micropython, and SPI is a built in feature. This was running on an ESP32 creating a WiFi to Gigabit Fiber bridge (obviously not at gigabit speeds).

I never thought it would be that easy, but it converted the task of writing something that does MDIO, SPI, and WiFi (with a webserver) in C, to basically a day of work.

Also the "feel" of running an interactive python shell on a tiny 1x3cm board as part of the initial bring-up process after manufacturing is just awesome. Controlling every IO "manually" via the interactive shell is so much better than seeing your prepared C code crash and burn, and only then start debugging it.