I bought under shared ownership last year. But I could only recommend it if you think the initial asking price is low (which I think mine was, so I'm hoping I'll make a profit when I sell to offset the rent I'm paying). It is a bit cheaper than a full mortgage, but not much more (for me it works out about �50 month cheaper on a �100k property) - and you're not making any profit (if there is any in the current climate) on the portion you don't own.
Shared ownership is great if you can't get a mortgage for �100k but believe you can pay it back, otherwise I'd recommend avoiding shared ownership. Unless you are prepared to take in a lodger I can't see that you will be able to buy. It's a horrible situation for all us first time buyers at the moment.
The only positives that might happen in the future are that the housing market could well start to dip because chains grind to a halt with first time buyers being priced out of the market, and the Government is encouraging builders to create more affordable housing.
Keep an eye out for schemes such as Debut (
http://www.debutbyredrow.co.uk/) - one of my friends got a flat for �55k two years ago. It's little more than a bedsit but it's a first step on the ladder and fingers crossed more house builders will follow Redrow's lead and build more of these homes.
Good luck!