According to Enterbrain, the folks who publish Famitsu magazine, the newest PlayStation Portable sold 28,275 units on its first day on the Japanese market.
That single day of sales doesn't tell us too much about the PSPgo's reception in Japan, considering Enterbrain only tracked one day, November 1, as part of its weekly sales monitoring window. As for how that compares to weekly figures, the most recent data we have is from sales tracker Media Create, which put non-go PSP sales at 32,865 for the week of October 19 to 25.
We'll have to see how the rest of the week shakes down, but won't have that info for a while, since Media Create's window tracks the same period
Enterbrain did note that the PSP had sold 12,797,180 units in Japan since the console's launch in December of 2004.