A tool that could do parallel downloads of small files would be a winner. We have a lot of small files and use s3cmd. It downloads one at a time. You can finagle it with some xargs magic, but it would be nice to have it built in.
s3s3mirror is great for this sort of thing (https://github.com/cobbzilla/s3s3mirror). We're able to sync a bucket with ~100k+ entries fairly quickly, so it's been quite handy for bucket backup purposes.