Another really neat twin LED system, but Cateye's focused output makes this a specific use special.
The two high powered LEDs both use spot lenses to give a really far reaching beam that'll out-range a lot of normal HID lights.
Unfortunately though, the beam is so narrow that it's not much use on technical terrain when bar mounted. It works great as a helmet lamp (mount is included) or a road light, though.
The Pro version gets a tiny solid block Li-Ion battery that can be strapped on almost anywhere or dropped into a pocket, and run time is ample for its size. Recharge time is very rapid (2.5 hours) too, so you can rejuice between laps if you've got a generator handy. The remote switch lets you toggle between power options to conserve life and it's also got a low power warning light.
The standard Double Shot has no switch or power change function and uses a heavier NiMh battery in a soft bag but it does shave a hefty £80 off the price at £170.