Not sure why that first paragraph was truncated :-P
Anyways, the difference in Linux support is that it's official...if you have a problem using it on Ubuntu, you can report it to Lotus Support and get help. Otherwise, they'd tell you the platform isn't supported.
For the server platform, Redhat and Suse Enterprise are officially supported, but it does run fine on Debian stable, Sidux (Debian unstable), Ubuntu, etc.

What makes this announcement different is

As for folks who use it for just email/calendaring, try using it for the secure rapid application development platform it is. Take your P.O. purchasing workflow, put it on Notes (securely and so your users can fill out info while disconnected on their laptops) in a few weeks.

Saying it sucks for email is like saying you really hate your spreadsheet because you're using it as a calculator and it's too confusing to use :-)

About time, I would say. I work in a company (large multinational) that uses only Notes for it's email and calendaring. Although I hate Lotus Notes, because I consider it to be one of the worst apps ever written, I can't see the company changing it's email-platform anytime soon. It's just stuff like Notes that keeps us locked in to MS Windows, although it's of course not Notes alone. A lot of in-house development is being done with .NET, although as a developer, I'm quickly turning away from lock-in frameworks. It would be great in some years to have the option of a Linux desktop instead. Hopefully BEFORE I'm pensioned! And I'm only 45...

Not sure what the big deal is. The usual practice, for other projects like OpenOffice, Apache, the Linux kernel itself etc, is to let the distro maintainers worry about it--you just release the source, and let them figure out how to package it appropriately for their distros.

Why couldn't IBM do the same? Then you don't need to specifically "support" Ubuntu or any other particular distro.