Is that the Notes client, or servers running Domino as well? Where can I find out more?
IBM's DeveloperWorks area seems to be down at the moment, so I don't have any links for you but you can search that area later.
The recommendations are for Domino servers. However, the idea is based on the notion that, typically, Notes/Domino databases are large and few in number (usually just a few hundred) so the space wasted by the large cluster size is worth the performance advantage. So I don't see why it also wouldn't be true for the client. However, an end-user PC is usually doing a lot more than just Notes and you can end up wasting lots of space.