Remote Desktop will handle all of that. It's very capable when it comes to imaging and rolling out machines. Ditto for software updates (you can also just have each machine check with your OS X server for software updates, instead of Apple's servers, and you can choose which ones to allow for download, but let the users do it at their convenience, depending on how you want to manage everything).
jW
(I realize you are talking small business, and this doesn't necessarily apply)
Let me preface this: I am in charge of 6700 OS X Clients globally at a Fortune 5 company. Compared to the 22,000 Windows machines we also support, the Macs present a unique and unrefined experience.
While I agree with you that the functionality is there -- Apple Remote Desktop does not scale to the enterprise. It does not compare to a product like CA ITCM (ITAM). Managing more than 150 workstations in ARD is a nightmare. Deploying patches to remote sites (a sales site connected to your datacenters via T1, for example) is painful without the ability to position a remote staging server. Each ARD installation is standalone.
Active Directory integration is weak at best. At random points, 10.6.x clients will fail to recognize AD Group based administrative privileges. One minute, you're an admin on your local box -- the next, you're not. Configuration stays the same. Using a third party tool helps -- Likewise has been the best integration we've used thus far -- but this is something that needs to be native and not tacked on.
Exchange support is also incredibly weak. Mail.app and Exchange 2007 is a huge step in the right direction, but very few Enterprises have moved past Exchange 2003 at this point. Most are skipping 2007 in lieu of 2010, and the only other alternative (while not directly Apple's fault) is Entourage 2004/2008. Both are pigs and are miserable in comparison to Outlook. Early testing of Office 2011 & Outlook for the Mac have been very promising, but it still lags behind Office 2010 in the Windows world.
Larger organizations that keep exchange accounts in a separate domain than login accounts run into issues with calendaring in the native OS 10.6 apps as well as in Entourage.
The Wireless Client on the Mac has severe weaknesses around 802.1x authentication. It does not integrate well with lightweight wireless deployments. Older access points don't support multi-cast DNS, which is required for Bonjour, and by default in a Cisco lightweight deployment these features are disabled. It's an annoyance but can be overcome at least.
Apple refuses to provide adequate support to the enterprise. They are so far behind in their enterprise support model, it will take one hell of an investment to put them on par with the rest of the industry.
I love Apple, and I deal with their shortcomings for a living. It just feels like they are so close to playing in the enterprise, but there's always a catch