I seem to remember (through my gin enhanced haze) that the first batch was around 500 units. I was number 330 on the waiting list and have a unit with a serial number of 47.
I have seen people suggesting that the serial numbers apply to the individual configurations of empeg (e.g. 4Gb Green), but I do not think this is true, no one from empeg seems to have confirmed this.
It appears (from what I have seen) that only about 1 in 10 of the people on the waiting list have been taking up the offer.

I have to say that I am very happy with my empeg (warts and all, because I know the warts are fixable via software).

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Unit serial number 47 (was 330 in the queue)...