building on the original poster's question, i've been looking into gravel/cx shoes a bit too. i've only ridden on roads and just starting to look into knobby tire style biking.
if i end up getting a gravel bike, i think i'd probably do 3-4 cx races a year too. so, i'm i OK with a mtb shoe? or do i need a specific cx style shoe to allow for the running part of the sport? or are most mtb shoes just fine for running up hills, mud, etc..?