Currently own a 32GB iP4. Because I am on Fido, the reservation system limited customers to 16GB. I didn't want to wait in line at the Apple store so I just went ahead and reserved one.
I spent the rest of the day figuring out how to get my 28GB down to something more manageable, like 12 or 14. Considering my music is 12GB, and my photos were 5GB, and all my junk apps put together were maybe 2GB, it turns out not to be as hard as I thought.
Photostream archiving helps a lot, but I'm a bit worried about iTunes Match. It's not that I think it's not useful. I just wonder how easy it will be to navigate my 111GB library on my phone in order to decide what to dl/stream.
On the plus side, the money I save by going to a 16GB will pay for 3 years worth of iTunes Match. So really, I'm not too worried about it.