The 2 largest electronics shops in HK are Fortress and Broadway [think BestBuy, CircuitCity, etc]. Service can vary from awesome to pathetic, same as everywhere int he world. Pricing? TBH, I have seen prices in HK for this stuff go way up in recent years. There was a time not so long ago where computer gear was noticeably cheaper in HK. Not anymore I am afraid. I bought an Asus laptop in HK that definitely cost me 100USD more than it would have in NYC/USA.
The big tablet players here of course are iPad and Samsung. BB Playbook isn't here yet [which, as a devoted BB user of 10+ years kinda ticks me off]. What are you looking for? In any case, Fortress and Broadway sound like the best bets for you. Good selection, multiple stores and yes, you can still haggle a bit if you choose [hint: hard cash is KING in HK]. Also, at those places absolutely zero fear about knockoff merchandise. They guarantee it.
Drop me a line via PM if you wish. Perhaps we can email and, schedules permitting, meet for drink/coffee when you get to HK. When do you plan to arrive and what district will you be staying in?
cheers and good luck and enjoy HK!
Pro-tip - getting hot and humid as hell here now so be advised