I think that Elgg has great potential, but to be honest I'm not entirely sure how to use it.
I dont know many people on the system and find it difficult to "make friends" as there is no direct interaction between users other than posting on their blogs, which seems a bit intrusive. Yet the potential to create a community out of disparate people with a common interest is Elgg's strength
One of the problems is that there isnt really a forum for direct interaction - such as a discussion space, a chatroom or a whiteboard, with blogs being used as the main expositive vehicle. Perhaps its my natural shyness
there is difficulty in knowing your audience with a blog.
Perhaps with a defined community (eg course group) set up in advance and taken in to Elgg, these issues might be lessened as the norms of the community and its objectives would be pre-determined, however to some extent that mitigates against the potential of Elgg for learners to create their own communities.
Use cases would be very welcome, as indeed would case studies. I also think that Elgg would benefit from some communication tools, such as discussion forum tools or chatroom tools inbuilt into the system, which I think would give people an opportunity to enter into the system and initially define their identity through dialogue with others.
Mhairi

Comments
I am currently working on some usecases which I hope will start the ball rolling. We have a series of pilots running - I will share the results of these once they are ready, again this might help people decide if Elgg is a tool they could use.
More on this later.
This is something I think could work very well - it is becoming clear that there needs to be a certain level of structure to help learners get into the system - my argument has always been that this structure should be provided by an individual (an instructor) rather than the system itself - the reason being, structure imposed by the system will go against the potential of leaners to create their own communities - they will only be able to do what the system lets them. Loose structure - or mentoring guidelines supplied by a course leader can help initially but will not be an obstacle if the learner wants to push the system to meet their needs.
It will be interesting to see what others think.
I found blogging to be a rather solopsistic endeavor until I started blogging with a specific intention. Put another way, I found I needed a goal.
Since I am a student in education (with a concentration in teaching and educational technology) I have used my blog to post my thoughts, concerns, and imaginings about education and technology. As such I have found people pop in and out, sometimes offering comments, which I find both useful and personally rewarding.
I like the fact that there is no clear structure in Elgg. It forces me to create one that suits me. I like to browse other users posts by going to the View All Posts section. I have made some wonderful connections this way. I don't find it obtrusive when someone I don't know writes a comment. I rather like it. But that's just me.
I have considered building a community in here for a particular class I will be working with and I'm still investigating how it might work. I also found that if I have any questions or concerns Dave and Ben are quick to respond.
I think that if you're shy you can still get involved. You have to do what's right for you. I encourage you to jump right in if you feel like it. People are rather friendly in here.
My experience so far is similar to what Chris has described. I find blogging a bit like talking aloud, rather self-consciously, and every now and then someone says "hi, that's quite interesting" and makes some, usually interesting and helpful and always friendly and supportive, comment. My problem is that I have a lot of different interests each one associated with a different group of friends or colleagues; I need about 6 different blogs! This is one of several reasons I find Elgg so good as you can start different communities rather than having to find a way of creating multiple blogs.
With group blogs like the communities, do we need something like discussion forums like phpBB?
I'm not trying to be confrontational here, it's a question I'm asking myself.
Grist for the "use case mill":
Communities are rather sketchily described in ELGG's help and information screens...now that I've discovered what they are through exploration, I quite like them.