I've got two of them an MR16 30W Hid and a MR11 13w hid both used on a mountainbike in the winter.
The MR11 would be ok for running lights as the depth of the beam isn't very far.
The MR16 are fooken bright and would be good as extra riding lights as the beam depth is very good. If you go for them then buy the spot bulb variation as the flood beam pattern goes every where and would blind everyone.
One advantage with these lights is that the ballast is built into the bulb so there's no need to have a separate ballast makes bulb replacement easier.
The bulbs are dear mind around £60.