Lowering the clock speed is a placebo, the Milestone ALREADY lowers the speed when sleeping by about as much as SetCPU would do, though it never drops down to 125, so that the phone will wake up fast enough to allow you to answer a call. As for temps, as I said, if you adjust your voltage properly, there is never any worry about overheating, it simply won't. If you're balls-to-the-walls overclocking and have a voltage-hungry processor in your particular Milestone, then it's a slightly different story. I think SetCPU was/is needed on custom overclocked Droid ROMs, because the way those ROMs are hacked for overclocking pretty much nukes the native speed management. But this kernel replacement .apk leaves the stock speed management intact, and SetCPU is then trying to override that. Also take a look at how much battery % SetCPU consumes in a day. Any savings you get with more aggressive power management than native could easily be offset by how much juice SetCPU needs just to run. Just try it for a couple days without SetCPU. I think you'll find that there are fewer "hitches" and slowdowns throughout the day (caused by SetCPU settings conflicting with native and polling overhead). And if you've dialed your voltage back as far as possible, you'll end up with the same or better battery life.