There's no need for you to install kernel-power, unless you need it for some reason. The kernel includes some bug fixes w.r.t. stock kernel, but as far as I can tell they don't concern major bugs (= the N900 runs still OK with the stock kernel For many people the main reason is overclocking/undervolting. Another common reason to use KP (only version 51r1 or 52) is that it allows you to run CSSU-thumb. Besides that, it may be relevant if you e.g. use USB host-mode and/or need kernel modules that don't come with the stock kernel.