IT show sells computers, laptops, printers, cameras, plasma TV, etc, mostly related to information technology. This year will be at Suntec Singapore and it's next week. Some of the items are sold cheaper than shops whereas others are sold at retail prices but included some bundled stuffs. Generally, its the best time to buy electronic goods.
Outside of the IT show, my personnel preference will be to shop at Funan where most stuffs have fixed price tags. However, you can always try to ask for discounts from the smaller stores, not major ones like Harvey Norman, Sony, Challenger, etc. I actually don't mind paying a bit more for quality service.
As for Sim Lim, it may still be a good place to get cheap electronic goods provided you can fend off bad sales tactics!! Go there to buy only WHAT you want, do not be swayed by the "bad" sales staffs who often claimed that the item you wanted to buy is out-of-stock only AFTER you paid the deposit and tried persuading you to buy other item at much higher prices! If you still want to go there, remember these: Don't pay before you have the item in your hand. Don't be indecisive, if the item you want is "out-of-stock", walk away. There is always another shop that will have stocks, unless you are looking for antique.