Purchased this because I was using one at my physical therapy after spinal surgery for a nerve injury that had left my lower leg not working for a month. The surgery was successful to restore proper movement, but muscles and nerves in my foot and leg need to be retrained. Balance needed to be regained, and home therapy continued "forever".
The board is very useful, and I have it out everyday to use, as I walk past it.
It is easy to use, and I have never felt that I was in danger of falling with it.
It has rough surface to stand on, so there is no way to slip on it.
I would advise that someone purchasing it, finds out EXACTLY what the purpose of the balance board is, and exactly what the muscles are that need to be worked with, toes, feet, ankles, lower and upper leg, knees, and lower back – and proper stance while on it. I was given careful direction at PT, but still am correcting some things that I didn't quite understand there.
It will be a regular part of the rest of my life, and it has helped me with regaining my balance.
It is a good value because I can do PT at home, and it is well made. It is not a ricketty product.

Very sturdy. Bought a cheaper one first, and retuned it when it made bad noises that first time I stood on it. This one feels safe with my weight on it. I think I could drive a car over it without damaging it.

Well made and solid. I use it to help strengthen my balance side to side and front to back. Great for the price. My only complaint is that for front to back it is a bit too narrow. If I try to stand on it so my hips are aligned to my shoulders it will flip up on the opposite side and creates a fall hazard. I have to get up with my feet closer together and then inch my feet out to the sides. Not ideal but it works. Seems like only the $100+ balance boards are square. All the affordable ones like this are rectangular. 2" wider would have made a big difference.

This balance board is very solid and very well made. It's 17.5 in x 13.5. The rocker part on the bottom does NOT go to the edges ( about 3 inches in on the 17 inch side and 2 inches in on the 13 inch side). When you put this on the ground, it can stand by itself. It has two rockers on the bottom which are joined by a solid piece of wood.
This is heavy duty and weighs 5lbs. You can turn it around (You stand with feet so that heels are near the shorter side) to rock/wobble/balance backwards and forwards vs side to side (stand with heels inside the longer side) . If you've been to PT, you know what I am talking about. So this board can wobble side-to-side and backwards and forwards.
Looking at some of the reviews, I want to add a few words: If you have good balance, this will probably be too easy for you. But if you have poor balance or want to improve your balance, this is a SAFE device. I have tried some of the round wobble boards with the single (curved) ball on the bottom and they present a challenge which is great but when you have poor balance, you don't want to break your neck trying to improve it!
This board is sturdy and feels very safe. I put it on thin type carpet and I have had zero slippage. The top is covered with a material that resembles the heavy duty sandpaper grit. It's great for me. It's not the cheapest on this site and I wasn't looking for cheap. I wanted safe.
Edited to add 4/19
I have central vertigo and I've made tremendous improvements in my balance after 4 months of using this daily. I watched the company video and am now working on turning my head and then turning my head and shoulders while balancing. Those are the next big steps.
The rocker board is by its design less unstable than a board with just one ball (wobble board). This wooden rocker board just gives you one plane of instability at a time. It does not have a 360 degree rotation which is far more challenging. Some sites say that a rocker board (such as the one I'm reviewing) is for beginners. Whatever. Bottom line: I'm not breaking my neck and I'm improving my balance.
I love this thing!!

This is a must-have for the stay at home work out! This is designed for a basic skill level and it is very stable. You will NOT fall off of this one. Excellent for doing squats and making them count. This immediately improved your balance and over a very short time improves your agility. My husband has low vision and can use this easily. It is improving his balance when walking, which is something that people with low vision have to deal with, this loss of balance and agility. There are numerous exercises that be done on this board, so take a spin on YouTube for some ideas. This arrived fast, in perfect condition and really sturdy and stable. I can't stress that enough.
Excellent Seller!

This is similar to the wobble board I used in PT for ankle exercises. Very pleased with the quality for such a great price.

Not as expected. The videos and photos are misleading. I was led to believe that this balance board rotates in both directions in one stance – sort of like a 360 rotation. It does not. I am disappointed. It's not challenging at all.