I would also suggest looking at existing code bases for examples of how to use them and the pros/cons of each approach. Again, I make heavy use of them in struct-plus-plus (struct-plus-plus/main.rkt at master · dstorrs/struct-plus-plus · GitHub) and a lot of what I use was learned from Alexis King's struct-update module (struct-update/main.rkt at master · lexi-lambda/struct-update · GitHub) There's a lot more code and varieties of code in SPP but SU does things that SPP doesn't. I haven't dug into the code for the various languages such as rackjure but there might be useful things in there as well.
EDIT: Oh, I misread the date on that last message as May 31. Looks like I'm necro'ing -- sorry for that, but hopefully the content is still useful.