I have been riding the O2 since April this year, what struck me immediately was the improved comfort and handling compared to my previous bike (Cervelo S5). The O2 is just as suitable in a fast group ride, climbing in the mountains or a long endurance event. It also looks much better in real life than some pictures suggest, the blue paint really catches the eye and draws a lot of compliments at the cafes.
If you are considering a new purchase you will not regret buying this bike.