Just got a 2007 Shadow Mica Sport a month ago !
I'd highly recommend the REAS. I test drove side by side with and without and the ride difference was noticeable. I really like the REAS.
That said, here are my only complaints about the Sport:
The seats: They are PWR seats which is nice but they are not leather and I really prefer leather.
Hood Scoop: overall it looks good with the Sport but does block a little view from inside and collects water while washing and drying.
Shadow Mica: Given the choice I'd go with Black. IMO the Shadow Mica is even harder to keep clean and get a gloss shine out of.
If money were no object, Limited would be my first choice tho the Sport is still a great truck.