i dont see the point in upgrading, if you bought the limited edition then you obviously can live without firewire, thats the only change which will be the dealmaker for most people holding off from the 13". 5 hours battery life is plenty but 7 is better, i certainly wouldnt turn my nose up at the 5 when many pc laptops struggle to get 3 hours.
processor bump will be like a 6% speed increase, ability to run 8gb ram is not of benefit to most as most wont pay for 8gb of ram or will have the need for it. by the time 8gb of ram is absolutely necessary i think the limited edition will be well out of date and in need of recycling