Have you checked out the FAQ? A lot of that stuff is covered there.
The impact on not having the slider is not as horrible as you make it sound. If you vote a lot, the system will automatically start voting with less weight, since your voting power will be lower. It is the same effect as using the slider, just without as much choice on which posts/comments it gets used on. When you have so little SP anyway, the effects of this are so minimal that most users will not notice.
The decision was made that it is not worth the extra complexity to new users, for the benefit they gain.