Well, a bit underwhelming.
More complicated to use than the MyHeritage clustering.
The Standard Cluster seems fairly pointless, as it really just gives close relatives.
The Custom Clusters are more powerful, they do let you see how your matches are related to each other, it simplifies what is otherwise a laborious manual process.
I have a large group of related people in Kentucky who seem to link back to a common ancestor in Lincolnshire, but has not generated any blinding revelations yet.
I have manually generated most of this cluster, and it is much bigger 130 or so versus the 20 odds that the Cluster settings allow you to see. The critical linking people between clusters often seem to be in the 10 to 20 cM range as far as I can see, unless you are very lucky.
They say that the clusters stick if they are associated with a group, not sure that is working, especially if you have pre-existing clustering.
The big benefit so far is the fact that it generates a nice picture and an easy to read list of people in a group, also that you can seem to be able to cut and paste the cluster into a word processor or excel. Libre Calc does not seem to work properly for some reason
Warning - note down who you have selected as the seed people for the cluster. You cannot edit the cM settings, or seed people and have to start from scratch each time.