I guess it depends what your expectations are buying electronics in Japan vs at home, which is the UK for me. I've bought three reasonably priced devices over the years :
Panasonic CF-R4 notebook: Tiny laptop with 10" LCD, 7 hour battery life, long before the current netbook craze started. Nothing that size or longevity available at home. (Of course, there's an abundance of them nowadays)
Sharp Zaurus C3000: Linux-based PDA. These models were only available in Japan.
Playstation 3: Available everywhere, but due to exchange rates at the time it cost £180 for PS3 + 1 game. UK RRP is still around £290 today!
If you have something particular in mind and the exchange rate is decent then buying electronics in Japan can work