very good but not perfect
As other reviewers have stated, this is a very solid accessory. It is a very useful and ergonomic aid for a D300/700 level camera and I prefer the mounting to that of the D200 and F100/F80 style (where you need to take out the battery door).

My main concern with this is that the secondary shutter release and the multi function rocker are not of very good quality. They don't feel similar at all to the ones on the camera.

Still, IMHO, this is a must buy for all D300 owners.

Great addition to a great camera
Bought this along with a D700 and I can't be happier. This grip feels like a part of the camera, not like a cheap add-on. Previously I had owned a Nikon D90 with the nikon vertical grip and it isn't in the same league. That one always felt cheap to me, like it was an after thought. You won't regret this purchase. It does add quite a bit of weight to the camera, but it's worth the trade off.

Get a Grip
I have to admit that, when looking at the Nikon MB-D10, I was tempted by the cheaper, off-brand battery packs for my new D300s. After all, at about 0, the Nikon MB-D10 had a whopper price, while the knock-offs cost a third of the price. But I'd taken the plunge on a new camera and wanted no worries about the accessories working seamlessly. How glad I am that I splurged on this battery pack! It connects flawlessly with the D300s and is a comfortable grip. I like the texture (which matches the camera). In the few weeks I've had the grip connected to it, I've already had several opportunities to use the camera in vertical position and the shutter release works flawlessly.
I think complaints about the grip's weight are unfounded. People like me, who have used the D3 (I have generally borrowed the D3 from my pro photographer friends) can appreciate that the grip makes my much cheaper D300s appear on a par with the D3. But it goes beyond appearance -- a primary reason I chose the D300s with the MB-D10 pack is the pack allows the camera to shoot at a speed of almost 8 frames per second. I love how this pack pushes the camera to greater heights. I have to admit that the first time I accidentally shot off a burst of about six shots I was concerned the MB-D10 would rush through the camera's expected lifetime of 150,000 shutter releases before my next vacation. But I soon realized it was helping me capture images I might have missed.
My next admission is that I have not tried one of the other brands for my camera, so I can't compare one vertical grip battery pack to the other. What I can say is that I am always comfortable paying more for a product in which I am confident.
The MB-D10 has not let me down.

Nikon MB-D10 The Best In Quality For Myr D300S
Texture of the body matches the same material used in my D300s. Very nice handling & looks gourgeous now like D3. Get it & you will say "WOOOWWWW !!!!!

Great Nikon Grip!
I've seen other aftermarket grips for the Nikon D300s and I can say that I'm happy that I bought the real Nikon one. The cost is a little more however it's built to last! I now shoot at 8fps. The buttons were a little stiff at first because it was new, but the more you use it, the better it feels. I great product that everyone should have!