In reply to avinash1981:
There are lots of bivvy spots on the actual ridge, especially in the first half. They may not be that comfortable, fit more than one person, or have water, but they usually have a dry-stone windbreak wall, and are vaguely flat. Most people seem to bivvy down in Coir a Ghrunnda (sp?), there are some springs there. When we did the ridge we had got all the way to TD Gap and looked down to see everyone still sleeping...
The Rockfax guide is very good but lacks detail in some spots (as you'd expect), but if you can see you'll be fine even if it takes a bit of a nose around to find the best line. There's a couple of spots where the scramble downclimbs are a bit tricky and I wanted a sling -but I had a knackered shoulder.
There are springs along the way, but you'll need to drop down a way -there's one below Am Bhasteir in Fionn a Coir (spelling!) side -look for the green moss. If it has been hot then knowing that is there can be a lifesaver