Check out the side streets and back alleys (Score 1)

Akihabara is an amazing place on the surface. But behind the neon glitze in the back streets and lanes are the cool stores (like the S/H MAC store filled to the ceiling). I agree with the other guy - I was just like his dad, facinated by all the little stalls that might have been selling anything else market-like but electronics was a real surprise. I think you could kill 2 days there, it's tiring..... But it was not really cheap (1.5 yrs ago)- mail order in the US was often cheaper. The only stores that do Duty Free are the glitzy ones and they are probably also the most expensive. Since I was there the Japanese economy has tanked somewhat so you'll probably get a nice exchange rate. (BTW Microsoft S/W is a bargain in Australia because they haven't increased their prices as our currency dived).