I happened across an article on a pretty interesting topic: a Lotus Notes client for Linux. Unfortunately, I think the author (and perhaps Big Blue itself) is missing an important point: Notes has always championed OS-independence. If you move a file using the filesystem, you are sternly reprimanded by Notes and told, in effect, that Note's way of replicating databases is vastly superior. For many applications, it is. You can practically live in Notes if your needs are well defined.
Which brings me to the perfect application for a Linux client: the call center.
Imagine hundreds of diskless Linux workstations booting into the equivalent of Linux Terminal Server or Knoppix for Domino. In fact, many different types of workers could handle all of their day-to-day tasks in this environment with substantial savings not only on the overhead of operating system licenses, but everything that goes with a complex user environment--like viruses, malware, and (worst of all) the myriad of operator errors that go with giving users too much latitude.
Personally, I'd like to see a Linux client to work in a more sophisticated way. But my hunch is that if and when IBM does decide to port Notes to Linux, a scenario like the one described above will be the impetus.