Something like this is always subject to individual preferences but here is my $.02 worth. I too considered an RT with the lowered suspension and if I would trade the ESA for lower seat height. I test rode an ESA model with the stock seat set on the lowest setting (32.2" seat height) and then with the low seat on the lowest position (30.7" seat height) and although I cannot flat foot both feet sitting on the bike, but I am not standing on my toes either, I determined that the ESA was worth a little higher seat height. I did not have the opportunity to test ride on with the lower suspension, but I doubt it would have swayed my decision. I purchased my RT with the ESA and the low seat on July 30, 2011 and have put on about 3500 miles.
I am 5'10' with a 30" inseam and commute regularly in to Washington, DC from Northern VA in stop and go traffic and so far I am comfortable with the seat height. If the seat height becomes an issue I may elect to get a BMW extra low seat (30.1" seat height) or other custom seat for commuting purposes.
In respect to the ESA I use that function all the time. My commute takes me over poor condition roads and smooth highways, while my fun riding takes me over all type of surfaces and I adjust the ESA as conditions warrant. To me the ESA is worth it and hope that more bikes adopt it over time.
I hope you find this useful. :bmw: