Caution: new traffic patterns ahead
Your network team may see different patterns of traffic thanks to the way that Windows 10 uses peer-to-peer connections to share updates with other users rather than having every PC download the same update individually. And while Wi-Fi access points that are on a domain-controlled network won't be shared with a user's friends, they will be over other Wi-Fi connections if the Wi-Fi sense option is enabled. This doesn't share the password, so it's not a security risk, but it does shift the decision about allowing access from the network owner to the user. You don't want unauthorized Wi-Fi hotspots on business premises anyway, so this is just another reason to check the network regularly.
If you want to manage Windows 10 PCs as soon as they start showing up on your network, you can do that with Windows Intune and other Mobile Device Management (MDM) services that work with the MDM client that's built into Windows 10 (offering features like conditional access, configuration management and remote wipe), or by installing the relevant service packs for System Center Configuration Manager. You need SCCM 2012 R2 or the upcoming release to deploy Windows 10 to devices, but SCCM 2007 can manage Windows 10 devices.
If the devices that users are bringing to work are running Windows 10 Home, they're going to be getting both feature and security updates applied automatically. That uses the same rolling deployment model Microsoft has for Windows Update today, where not all PCs get the updates immediately in case there are problems.
Without the option of turning those updates off, the PCs that show up on your network are likely to be more secure. There's always the possibility that a problem update will affect your users and generate support calls, and if updates are labelled as cryptically as the hotfix bundles released for the final technical preview builds (which have no details of what fixes they maintain), troubleshooting might be more complex. But this is unlikely to cause significant problems, and it won't affect Pro and Enterprise versions, where you'll be able to control update deployment via Windows Update for Business. You can also opt for Current Branch for Business, which gets feature updates some months after they've been tested through the Windows Insider program and consumer installations, making it far less likely than any automatic updates will have problems by the time they reach your PCs. With Current Branch for Business, you can also postpone updates for up to eight months.
Paying to be up to date
Windows 10 marks a good time to think about Software Assurance. If you have SA, the upgrade to Windows 10 is included although you will need to maintain your SA status. If you don't have SA, you'll be able to buy Windows 10 Enterprise licenses in the usual way, and the in-place upgrade option may prove less time-consuming than the current option of wiping and re-imaging systems (you'll be able to deploy apps and configuration settings as part of the upgrade). But if you don't pay for SA along with those licenses, you don't get the same regular updates that Home and Pro users get for free.
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