I bought two of these helicopters. One for me and one for a sibling. We have owned them for about a month. They both work great.
What's good about them?
They are a blast to fly. Chasing the dogs around the house is hilarious. They are easy to control, but not boring to fly. Cruising around an open room is easy even for a elementary school aged child. If you want a challenge, try landing on small objects like stools, ceiling fan blades, window sills, etc or manoeuvre under and around furniture. They are very durable, which is good because you will crash and drop this heli. Mine has suffered an average of 4 crashes each flight. Whether it's plowing into walls, people, ceilings or furniture, it has always survived the fall to the tile floor. The only piece that broke was a fail fin. The plastic blades are made of a lightweight plastic that is pretty safe in terms of colliding with humans. I've been hit by the blades and it has never left a mark on me. Some may say it will hurt on occasion, but it's nothing that lasts or is worth crying over. When charging the heli, the USB charger and controller indicate a full battery with a light.
What's bad about them?
The flight time is limited to around 8 minutes (you should stick 5 minutes to make your total batter life span longer) while charging takes 40 minutes. Although repairing plastic parts is pretty easy, replacing electrical components look somewhat difficult. Obviously as stated, this is an indoor heli. Direct outdoor sunlight will make controlling your heli difficult due to the infared signal. Also, even a 1 or 2 mph breeze will carry your heli away.
The two helicopters I purchased were not perfect, but had some issues. My helicopter has lower blade shaft that wants to stick. Probably needs some oil in the gears. It flies perfectly, but you can tell that the friction slightly shortens the battery life compared to my brother's helicopter.
My brother's helicopter won't remain stationary when attempting to hover. It is off balance somehow and it makes a circle around where you are trying to hover. Usually about a 3 foot diameter. The orientation of the helicopter stays accurate but it strafes around in a circle, making precision landings difficult.
I have seen and used other s107 helis that have worked perfectly. I recommend this helicopter for just about anybody.