I had a SYM RV-250 and made the switch to a DT-300. Like others have stated, the DT seating is not the best for taller riders. I'm 6' 1" and I liked the RV-250 ride much better. I like the acceleration and overall handling of the DT a little better but would like to stretch out my legs. I've been on some longer rides (over 2 hrs) and it's not that bad. I do tend to slide forward during in town trips and especially so on bumpy roads. But for the price, gas mileage and performance, I really like the DT.
In an effort to improve my seating, I had the seat "adjusted" to give a little more room in the back. Despite gaining another inch, I'm still a little cramped...although I like how it looks. Here is the new seat with a comparison to the original one.
(New seat)
(Original seat)