It seems I'm always a step ahead of everyone else when it comes to wetsuits-- I wore a suit all year this year (summer time I had a short sleeve full on nearly every day with an exception of a few days trunking it).
It's not necessarily the water temp that makes me cold, but the air temp really gets to me. I'm already considering a 4/3 if this air temp doesn't warm up soon. Given I'm a smaller guy with practically no body fat, I wish I had a higher temperature tolerance.
I'm not sure if it's a "I'm too tough" mentality or what, but I'm not afraid to slip into a thicker suit early on.