Think of it more as currently in the shape of a data warehouse (which it really is). Most data feeds into data warehouses aren't that great - they need to be massaged into something useful and Google are finding out over time what the problems are.
If you can't find something in a database, it significantly decreases the usefulness of having all the materials there in the first place.
That's true but not to the point where you'd consider not making any of it available until it was perfect (or most of the way there). It's not perfect and it probably never will be - given time as they find more systemic problems in their metadata feeds and address them things will get better. They may be at 90% but for most people it's going to be good enough as it's more than likely going to be used like a library browsing sections for interesting things.