I suggest changing the SP system so that you don't expend any Sp while travelling unless you wanted to introduce a travel system where you can skip to a location for SP and travel on foot without using SP. Just a thought
I'm going to have to echo the previous comments and say that yes the game is good and interesting but the SP system ruins some of the fun. It is a flaw that exists in many similar games and while I understand that one of the games goals is to make money, I think that the SP system is too restrictive after you've advanced past the fist few levels and continues to get worse the higher you level up. Apart from that this is a great game although most likely I will only play it for the rest of the day or maybe for a few more days but then the SP issue will get too much and that will be the end of the game for me. I am sure that I am not the only one that is in this situation.