What enterprise virus-scanning systems do you recommend?
We use McAfee and I would warn you from using it. It is veeeery slow. Previously we had AVG and it was much faster.
Edit: Oh, and it has deleted my 'bluescreen' screensaver from sysinternals. One day it popped up the window saying a virus with category 'joke' will be deleted. No options to ignore and keep it...
In the past I have used Symantec Corporate Edition quite extensively. Whilst their Norton products have a bad rap (for good reason) for being slow, the corporate version was pretty quick and unobtrusive and had a good managment console. However that was a few years ago so they could have ruined it by now.
I've recently had to use kaspersky and I don't recommend it from what I saw. It may have been the version I was given but the centralised management features were a bit of a joke.
avast! Professional Edition has some nice features like creating a preconfigured installation, background scanning (doesn't hog the hard drive while the computer is under load) and can be configured to be user-friendly in not dropping millions of notifications on him. There are some server products avast! authors offer, like avast! Distributed Network Manager.
At my side IT job I only used the client Professional Edition, without the management server or DNM and it worked very well.
We have stopped recommending strict anti-virus software, and have moved to anti-malware at this point. Centrally controlled/distributed is a must. I agree with some of the people here that McAfee and Symantec have just gotten out of control with their bloatware. We have found a lot of success with F-Secure. It has a nice interface, not too heavy, the centralized management is pretty good. It covers viruses, spyware, internet usage, email, etc. Their support has been good so far and deployment has been pretty straightforward. We have it setup on a few networks. Since you are going to need something that works for your environment, I suggest you setup some virtual environments and test each of your candidates out, especially on the user experience side, I would guess you want the least intrusive software to minimize desktop support questions. Good luck!
I always use Malwarebytes for spot removal since it just seems to remove what Symantec often can't - has anyone tried the pro version? The site doesn't list any centralized management features...