I noticed this difference between the Kindle 2 and 3. With the Kindle 2, sliding the button and holding for 5 seconds would turn it off (rather than just putting it to sleep). Then a slide and release of the button would turn it back on within a second or two. The Kindle 3 has a 15 second hold to turn it off, and it takes a long time to restart - maybe 30 seconds or more. Needless to say, I don't bother turning off my Kindle 3. There doesn't seem to be any point anyways. The battery life is so long it took 6 weeks before my mom noticed that she had left her charger cable at my place (she spent Christmas here and I gave her a Kindle 3 as a present).
Linda