We bought our two bedroom semi via Orbit last year. Before that, we lived in a rather unpleasant HA flat, in a bit of a rough area. We wanted to buy our own place but struggled with saving a large enough deposit, everytine we thought we were close, house prices kept going up.
S/O wasn't something we had really looked into, we sort of stumbled upon it when we found a new build development we liked. Orbit was offering new build two and three bed houses on the development so we looked into it.
We saw plenty of horror stories but I think if you go into it informed, it's not an issue. For us, we intend to live here for a long time and we hope to staircase to 100% in a couple of years.
Re the price, our two bed semi was just under £170k which I thought we good, as we had been looking at other houses of the same size and spec for £180k.
The house itself is wonderful. The rooms are large, the garden is large, we have a huge driveway for four cars.
We do pretty much what we want with the house, the only thing we would need to ask permission for would be structural, say we wanted a conservatory or something.
Orbit were pretty good throughout the process, however I found it stressful from start to finish. With Orbit, you have to apply for the house in the same way you do for HA properties, they go on a website and you bid (for us at least, as the council had a say in who got them). We had to qualify and there were lots of criteria, couldn't earn more than £60k, couldn't be a homeowner, had to have connections to the area, had to currently live in the area (we didn't though). The Council then shortlisted who they want, for our house, 46 people applied. Orbit then go through the list in number order, seeing if the people are eligible for S/O and seeing if they can actually get a mortgage, etc. Luckily for us, we weren't near the top of the shortlist but all the people below us either couldn't get a mortgage or didn't realise it was S/O 
We purchased 60% of the house, paid a 5% deposit. Our rent portion is just over £100 a month so it's not expensive.
If it wasn't for S/O, we would still be in the manky flat!