Gah! Why did I read that 30 minutes after succumbing to the temptation on Steam? I've put in a refund request. Given the purchase hasn't even been processed yet, hopefully they'll approve it.
I also nearly gave in to a Steam controller, but in the end I stuck with the trusty Xbox360 one.
In case anyone else made the same mistake as I did - Steam refunded my payment immediately without complaint, so I could order from Play instead.