Lifehacker has done their own testing in a comparison of notebook battery usage in sleep mode. While hardly an exhaustive test, they did put a few different models through the challenge, including a new 15″ Macbook Pro and an ASUS Eee PC.
The report is, to put it mildly, dry, but battery testing isn’t exactly exciting unless you’re trying to determine how much juice is required to make them explode. Short version is, on practical level, sleep doesn’t draw enough power to worry about during a normal day. In one case, the power consumption of shutting down and starting up a laptop actually outweighed the consumption of sleep and resume. I’m sure most of us here have come to similar conclusions during our own usage, but the data is there on Lifehacker if you want it.