I find the Doc Mapper an incredibly useful tool and very unique amongst other review platforms. Instead of charts, lists and numbers, it presents the documents in a visual form with a coloured dot representing each document (the colour representing the responsiveness selection that has been made), grouped together in spiral clusters of similar documents. Thus if the document in the centre of the cluster is not responsive and the one on the outside is not responsive, it may be safe to assume the whole spiral can be bulk-coded. Or you can change the colour coding to represent different parties' productions so that you can see where all parties produced similar documents, or whether one party produced significantly more or less in any one topic area, which may provide insight into other parties' case strategy. It takes a bit to get used to using a very different approach, but a user can also map any group of documents (max 10,000 docs), so for coding a batch, you can sort it more and more specifically into similar docs, which makes review more efficient and consistent.
The security settings often have too many different things that need to be altered for one thing, making case administration tricky. In trying to make it do everything that anyone might possibly want, it becomes a bit unwieldy. Also there's been some rocky transition in merging the old Ringtail with the former Attenex, but that is gradually getting smoothed out with each release. Administration is significantly easier with 8.4 than it was with 8.3. Looking forward to 8.5!