In reply to Doad13:
I haven't used the app, but I'm an admin for the UK area of their site. In general the quality is really mixed, since all the areas and routes are submitted by users. Some people do a really good job of it, providing a lot of information; others just copy a line or two from the guidebook, which isn't really enough.
I would warn you that Mountainproject is primarily a US site so while 19'000 climbing areas sounds impressive, it's quite lacking in the UK. Certainly not a guidebook replacement here! I try to add areas/routes to the site as I do them, but it's pretty slow progress.