I develop a new website and I want to use GridFS as storage for all user uploads, because it offers a lot of advantages compared to a normal filesystem storage.
Benc
As mentioned, it might not be as fast as an ordinary filesystem but then it gives you man advantages over ordinary filesystems which I think are worth giving up a bit speed for.
Ultimately, with sharding, you might reach a point however where the GridFS storage actually becomes the faster option as opposed to an ordinary filesystem and a single node.