Linux is a great choice for SMB
Linux can be a wonderful, cost-effective operating system that can save most small businesses a lot of money in licensing costs AND consulting costs as well. It's my feeling that a staffed IT department is more necessary in a Windows-based server environment than a Linux based environement because Linux is much more stable and trouble-free.
For instance, compare a Linux machine acting as a mail server in a small business organization vs. Exchange Server running on Windows 200 Server. With a Linux machine configured with, say, Postfix and Cucipop it's a fair statement to say that the machine will run for about a year or two before it needs even a reboot. If you were to install Fedora (the offshoot from Redhat) you can configure it to get its own patches automatically. With Exchange Server, there needs to be patches applied, the system itself will likely require attention throughout a given year, and the licensing costs are significant. Either way, most people will need professional help to install the Operating System and the Mail Server software. Why not choose an OS that is stable, trouble-free, and FREE. There was an earlier post that said that the installation of Linux is neither free nor easy. I beg to differ. I have installed dozens of Linux machines and I have never paid a dime for any software related to Linux. I don't even pay for the media, because I do FTP installs. It's also a trouble-free installation. You can literally walk away from it.
In all, I can't see how a small company wouldn't want to use this superior operating system.
Build to the strengths of Linux
It is easy to argue about how "Linux" will not take the place of "MSWin", because the best of both rely on completely different structural models.
To realize the greatest benefit of Linux in the enterprise it is important to emphasize the benefits of the inherent architecture of Linux.
Leave your preconceptions behind. Rather than force Linux into the Microsoft mold, build a system for a small business based on Linux in its strongest form: Thin Client.
Each client machine acts as little more than a keyboard, mouse and display. A 9 year old Pentium-100 will work just fine, so any PC purchased since 1995 can be utilized. There is no need to upgrade hardware just to keep up with OS Bloat.
If there is a failure of a Thin Client, there is no company or personal data lost. Cheap spares are easily maintained on hardware that less efficient companies throw away as "obsolete".
The server is the only machine that needs to be big and fast by present standards. Even so, because of the inherent frugality of Linux, what presently constitutes a "desktop" machine can support many active clients and users at once. High availability and redundant hardware can be used cost-effectively if needed, because it is only used on one system. If load does become a problem, upgrading hardware is easier because, again, it is only one system.
Each user is defined on the server, all applications are run on the server. The user has the same files, icons, applications, settings and functionality on every client, or even when connecting remotely.
There is only one installation of any application, for example OpenOffice.org, on the server. There is no need to deal with a separately licensed office suite for every users individual machine. This is the "free as in beer" part.
System administration and security are simplified dramatically. There is only one file system to backup and one set of applications to keep up to date. There is only one system to harden against cracking since no company data (not even usernames) is kept on the clients.
Firewalling is simplified, since there is only one system, the server, where the users will run a web browser or other network application.
Non-business applications like games can simply never be installed in the first place. The inherent separation of user and administrator privileges makes surreptitious installation of spyware, adware, viruses and trojans far more difficult and virtually useless anyway.
Display managers like KDE and fvwm provide an interface which will be familiar to anyone who has used MSWin or MacOS. Or, an extremely simple, resource frugal and fast display manager can be configured to offer only those applications and functions specifically needed for business use. Different display managers can be used by different people at the same time, so a person can be comfortable regardless of their computing background and skill level.
There may still be a need for particular applications that will only run on MSWin. Win4lin, Wine, FreeDOS and the other emulators allow these too to be run on the server and displayed for whatever user needs them.
Lastly, for the user who still wants to use a MSWin "desktop", there are several software packages available that allow the Linux server to display fully functional "windows" on MSWin. Integrating a MSWin system into a Linux server environment is seamless. The same goes for MacOS. Many Open Source applications, such as OpenOffice.org, are also compiled for MSWin and MacOS, further easing integration.
In every practical way, Linux benefits the small business.