This is "old" news (from 2005), but it summarizes everything. I followed
threads from Slashdot about Ubuntu into what is good for desktop usage.

The Open Source Development Lab (OSDL) made a survey. Also there was a
survey in 2003 and 2004 made by DesktopLinux

From 2003 to 2004, Debian lost its gold medal lead and it became an
equal battle with Debian, Mandrake, SUSE, Red Hat etc.

From 2004 to 2005 Ubuntu seems to have caugt up (it's just as new as
Zenwalk, BTW - it started in 2004). It looks as if Ubuntu sucked some
users out of Debian, but that's not the whole story.

Summary:

The most critical applications for successful Linux deployments (enterprise, SOHO = Small Office / Home Office usage),
according to the survey takers, are email, office suites, and Web browsers.

OSDL said it is interesting that email is being considered even more
important than either a browser or office productivity. Rosenberg
speculates that that might be because "email truly is the killer app
regardless of platform," or that desktop Linux still needs a quality
email application.

The 13 page report also gives us the following answers:

no 1. Email client, rated critical by 62%
no 2. Office, rated critical by 51%
no 3. Web browser, rated cricital by 50%

Development tools rank no. 5. (Database applications is no. 4)

Most important browser plugin is Shockwave / Macromedia Flash. Second most important is PDF reader (specifically Adobe Reader, but lets not value this rating too hard - any PDF reader should do, if it works good).

Regarding "required natural language support":

English = 80%
German = 14%
French = 12%
Spanish = 12%

Not surprisingly, english is dominating (some respondends must require more than one language since the number adds up to more than 100%).

Regarding areas of Linux - Europe (44%) and America (37%) are by far the most important markets.

Conclusions?

Regarding email clients. I personally feel it is because email clients are not good enough, yet. I feel that Zenwalk gives a good compromise with Thunderbird, but that Sylpheed and Evolution could be offered in the Extra section (giving users the option of either downscaling or upscaling).

With Zenwalks "one app per task" philosphy it becomes quite important that the best choice application is chosen in critical areas - or that alternatives are provided. I don't doubt regarding Firefox, BTW, that it is a best choice.

Personally I have doubt about the "Gnome-office" suite (Abiword and Gnumeric), but providing OpenOffice in the Extra section works for me.

The language analysis indicates that english is the language. Other languages can be chosen as "natively available" but be aware that such work should not be a main focus. Since end users weight english so high and other languages so low a distro will not gain a lot from adopting multiple languages.

What was most surprising to OSDL was probably the top two reasons given for deploying Linux on the desktop - it was 1) employees requesting Linux (user demand) and because 2) my competitors have successfully deployed Linux.

Personally I see this change as - now it is no longer the "tech leaders" that do Linux - but also the "followers" (those who copy what the leaders do) - in marketing called the band-wagon effect - people jump onto the band-wagon - they follow the stream (as opposed to leaders, who can sometimes go against the stream).

Links:

Regarding OSDL survey : http://www.desktoplinux.com/news/NS5481370522.html

http://www.osdl.org/about_osdl

Older surveys:
http://desktoplinux.com/articles/AT2127420238.html

Enjoy,
Claus