Well, as far as I've read, most stores had it for pre-order purchase only. Also, while I barely check 2ch, I did it just now to see what was going on and there was one DSi thread but without many replies, and most of them were talking about how the DSLite was better because it's cheaper and it has GBA retro compatibility. In fact I was thinking about getting the DSi but seeing how GBA games won't work, I just rather wait.
Anyway, DSi will probably start selling like crazy once they start releasing software specific for it (something on the lines of a digital diary where you can add the pics you take with the cam, maybe?). But let's wait for the month sales to see how it really did.
Btw, in my class (design) there are at least that I know, 6 japanese boys and 3 girls with the DS, out of 23 students. Two of them are always playing GBA games (as I do. Right now I'm with Super Mario Advance 2 (SMW)), the other people are either playing the new Pokemans or some rpg. And out of the 6 I've asked (my friends), none wants to get the DSi, lol.