I have a late 2009 white macbook and have been using it for more than 5 years. Now it is extremely slow. I need to buy a new computer badly. I want good performance. Is the 2015 13" rMBP good enough to buy? Which model should I buy? Is it worth to buy the ultimate configuration? I suppose I will use the new computer for many years. Now the 15" is not in my consideration because the configuration has not been updated. The 13" has faster SSD, a new trackpad and longer battery life. Please give me some suggestions. Thanks.