Given the age of Star Wars, and the simple fact I'm interested in military stuff, I always imagined that cloaking device was:
a) a stealth technology; however, stealth is achieved through angular forms and special coatings (unless the Russian concept of plasma "bubble" proves effective)
b) heat dissipation technology - that's a bit Mass Effect, but ships with immensely powerful engines and reactors, plus heat based weapon systems would emit a lot of heat, easily visible in the cold vacuum of space; "cloaking field", as in Star Wars, I would imagine is either heat absorbing cells that can store the heat for a while, or a complex system that dissipates heat very fast. Either way would require a large ship to house it.
For one, I would really hate to see the visual "cloaking-decloaking" sci-fi cliche in Star Wars. :/