I got mine in January. When it was around 20 to 30 degrees below zero (F.) and I was letting it run for 5 minutes before driving (because I'm a wimp and need to get the cab warmed up a little bit) and then running the heater on full blast (so the ICE never shuts off) and my typical commute is ten minutes so fully half my driving is in Phase I, I was getting 29 mpg. I presume this is the worst possible driving conditions and so is probably the lowest possible mileage for the Prius.
Now that warmer weather is here (50 to 60 degrees F.) I'm getting around 43 or maybe 44 mpg. I still have a very short commute, but the ICE warms up faster in the warmer weather so Phase I is shorter.
For what it's worth, I'm seeing phenominal mpg numbers after the first 5 minutes. I often see 60 to 75 mpg in the second 5-min segment. And once, on a longer drive, the third segment showed 100 mpg, but the SOC had gone from 7 bars to 4, so that doesn't really count. If my commute were half an hour instead of ten minutes, I bet I'd be getting darn close to those advertised EPA figures.
My driving style is Just drive it!