I got a d3r as an experiment.
For the money, it's an excellent performer. Finish is not as good as on some of the more expensive engines, but that doesn't really matter. The engine runs fine and despite what some say I find it very easy to tune, even with the stock carb on it. Just adjust in small amounts (1/12th of a turn) and it should be fine.
The engine has a lot of torque at the bottom end, but is lacking a bit at the top end. It handles high gearing great though, so I get my speed that way...