I picked up a Vello brand grip used from a fellow Nikonian and it has worked very nicely. I like the additional size for handling the camera, but, I believe the additional battery is unnecessary since the D7000 batteries last so long. Others have commented on breaking the battery tray toggle, but I can't see that happening unless you are overly ham-fisted with it. One of the best bang for the buck accessories I have purchased. No complaints.
I bought one off ebay for $35 inc shipping... Took 2 weeks to arrive, was reasonably well packed... Have had it for 3 months now, use it for outdoor sports photos and occasional indoor sports, so gets handled quite a bit on the D7100.... I use a 70-200 2.8 Sigma lens, so a decent amount of weight on it and I clip a rapid strap via the tripod screw.
I agree you have to be careful with the battery cover lock/toggle, but otherwise been very happy with the quality and the savings!! And for me the extra battery is definitely a plus, I use continuous focus and am ususally out 3-4 hours in the field, so battery drain and hundreds of photos means I can keep going without worrying about power....
I want to spend my money on lens and other accessories wherevthere are no third party alternatives (cheap ones), so savings here count for me!
If you want a genuine Nikon grip, I have a very gently used one which we might be able to come to terms on. I won't let it go for the cost of even a "pricey" knock-off, but I can try to make it attractive. Email me if interested.
I purchased a new Vello battery grip for my d7000 and could not be happier with it. It feels great on the camera and functions as expected. No problem using camera on tripod with the grip on. I appreciate that I have choice to use regular batteries in the grip, but have not tried it. The button on the grip in portrait mode is something I use often and appreciate. (Note: Hi, I am new to the Forum _
B&H, which is about as reputable an internet seller as there is, treats the Vello products like a reputable line. There is a page for them in B&H's hard-copy catalog, and they are all over their website. This gives me a little more confidence in this third party seller than I would typically have. They aren't trying to hide it like some cheap Chinese piece of plastic knock-off.
There was a time I would never have considered putting a third party grip on a four-figure camera, but a friend of mine has been using a Vello grip on his D7000 for a year, and LOVES it. B&H is selling the Vello grip for the D7000 for about $69.00 (same as what they are discounting the D7100 grip to, right now). For that money, if it fails, you can buy a new one two more times for the price of one Nikon grip - and have a few bucks left over. So long as it doesn't fry the camera's electronics, it sounds like a great deal.
And, no,…I haven't heard any stories about these grips frying the electronics. What I don't know, is if everything functions exactly the same. I've heard stories in the past about command dials functioning backwards on some of the third party grips, but I can't say I've heard that about the Vello grip.
My experience is actually with the D800 but I think this part might be relevant. I use the SpiderPro holster. It's great for hands-free walking, hiking with the camera on the hip. Very convenient to unholster, shoot and replace. I've read in other threads that the after market battery grips are not as solid. With the Nikon battery grip on my D800 and 2.8 glass attached, the weight hanging down is considerable. As I rest my hand on the camera I can feel the battery grip flexing slightly in rhythm to my steps. I would think that the less solid after market grips may not feel as secure.