I have been driving a bullet 350 standard petrol version for the last 5 years and recently added up a diesel bullet to my stables. The machine is definitely sluggish when compared to the petrol version. However, you can do a 0 - 60 under 15 seconds, which is quite ample for city drive conditions. With the right mechanic, the vibrations associated with a diesel engine can be cut down to a large extent. Gear Shift is equivalent to that of the petrol version as there is no change in the gear box.
A smart mechanic can even adapt the newer 5 speed gearbox assembly to go along with the vehicle. This vehicle gives you the liberty or flexibility to chop and change various ends to suit your styling and comfort needs. Mielage is a definitive plus - currently enjoy 60+ km on a litre of diesel. Maintenance costs are less as compared to a petrol engine. If you can lay your hands on a good mechanic, and have the time, patience and passion to put together a vehicle to match your tastes, this is it. The only negative that I can come up with is the heat that is generated by the engine on long drives & the engine noise levels are higher.