Summary: Having used it with my Nikon D2X I wish I had not traded it with the camera when I purchased the D300. It works well and does a reasonably quick charge with the Nikon EN-EL4a battery which I now use with the Nikon D300.
Summary: Hard to find flaws in a charger that charges as expected and works like a charm. I bought a second one of these because I wanted to be able to charge 2 batteries at a time, or take one with me and leave the other at home. Nikon also sells a dual charger like this, but I prefer the items separate for those just in case moments. I've only recently started using Nikon gear, and am very much impressed with everything I purchased.
Summary: Obviously a sophisticated piece of equipment (based on the price). Easy to to use and fast. Expensive when you add on the cost the battery and the adapter for the MB-10 grip. Another example of the Nikon add on - add up product strategy.
Summary: You need either this charger to charge EN-EL4/4a batteries or the MH-22 dual charger. This to my mind is the more practical of the two. It is larger than previous chargers, making packing for travel an issue. Lights on charger are useful, reflect charge percentages 50/80/100, as well as calabration lights.
Summary: If you use a D300 with the MB-D10 grip and switch to the EN-EL4a batteries, you'll need either this charger or the slightly larger MH-22 dual battery charger. Both are fairly large when compared to the chargers for smaller Nikon batteries, such as the EN-EL3e, so for travel they are a bit bulky. However, the additional status lights and option for battery conditioning is a plus.