I think the hardest thing about Flickr is finding new interesting groups and inspirational images. Flickr isn't so much a community as a massive collection of little communities, surrounding individual users and niche groups.
Finding new stuff on Flickr is one of those 'don't know what you don't know' situations. How can you find something new when you have to tell it what to look for? If you can think of the term then you pretty much already know what you're going to get!
And then there's all those great groups where the name of the group is poetic and not something you'd ever search for. (Shame "Awesome Photos" doesn't really bring up awesome photos)
So, what are your interests?
what do you search for?
what are those phrases that turn up gems?