1) The statistics show, over time, whether you're improving or not and you'll be surprised it's not necessarily the areas you think you need to improve! It's certainly helped me.
2) To know what you achieve against given (or self-inflicted) targets is far better than guessing.
3) I have found Scoresaver 2 encouraging as it breaks each round down to into its constituent parts and, although my driving may have been abysmal, it's great to now that my putting has been 'professional'. It's a massive fillip!