I've had the chance to play around with Delicious and had little difficulty uploading bookmarks from my computer onto my account. Finding other people is very tough on it especially if you want to follow your friends and colleagues and their use.
I find that there isn't much that you can do with it, apart from it being a central database of all your bookmarked sites. You cannot even organise your bookmarks into folders etc to make locating websites easy. I think you would need folders if you want to maximise its use in the classroom given that certain websites would be relevant to certain subjects. Having it one just one list would make it harder.
Given the limitations, I wouldn't recommend it for classroom use at this point in time.
