I've made WP_Object_Cache multi-blog aware which should hopefully fix the problems with member blogs having the blogname of the first blog and other strange issues:
http://trac.mu.wordpress.org/ticket/61
http://trac.mu.wordpress.org/ticket/72
http://trac.mu.wordpress.org/ticket/67
drmike - can you update the confirm that these problems go away? (hopefully!)
Also, if you're using memcached, you will probably have to make a similar change to it's object cache as they appear in this changeset:
http://trac.mu.wordpress.org/changeset/650