Pros:

Mostly flat – pro for me, but I know some people (like my crazy husband) prefer hills
Accessible – parking was free, not too far away, and I didn’t get my car towed
A human dressed as a dancing cow– seen throughout various points of the course
Cowbell – and it was pink!
New Town – distracting by its quaint eeriness or eerie quaintness
Ring the bell photo op – if you PR—or just take your picture with an enormous cowbell, which is still fun

Cons:

Risky weather – could have been in the upper 70s in St. Charles this time of year, although we had absolutely perfect weather
Poorly designed starting corrals – can affect your starting mojo (or if you need something to slow you down your first few miles, this could be a pro, because some people come out of the gate way too fast)
Few spectators – if you’re an attention whore
Sketchy support with the water teams – potentially corrected next year and not a problem if you’re fast and get there before the water runs out!
Scenery – it’s mostly meh

Final verdict:

I would run the MO’ Cowbell again, especially as a St. Louis area resident looking for a fall half marathon. If you don’t feel like dressing up for the GO!’s Halloween race and you don’t particularly care for a different cover band playing subpar music at every mile a la Rock N’ Roll, this could be your fall staple. If you’re coming in from out of town, there is plenty to do in St. Louis that is free or super cheap; we are becoming a foodie mecca (for real!); and the race isn’t so crazy big that it’s intimidating. It feels like a hometown race done on a bigger scale but not too big.