I normally would go with the 16GB. I'm known as a cheapass and, ironically, I don't really have a lot of funds right now (you'd think I would, given I'm a "cheapass").
Anyway, I will be shooting for the 32GB for the first time actually.
The main reason I am doing this is because of my experience with Google Music All Access on my Galaxy Nexus 16GB. I've found that I really enjoy using All Access to its fullest abilities, and that means I'm finding new artists all the time and pinning them to my device for later playback. Photos are backed up via dropbox or even google+'s built-in solution, and everything else is fine...but hey, extra storage isn't a bad thing, and I want to be able to pin music to my device without first being hesitant and checking "available storage" like I've had to with my Galaxy Nexus.