Microsoft release Hyper-V Integration Services 3.3 in June, and they officially support up to CentOS 6.2. If you try to install them on CentOS 6.3 using the install.sh script you will recieve the following error:
kernel(clocksource_register) = 0xd88be65d is needed by kmod-microsft-hyper-vrhel63.3-4.20120605.x86_64
The problem here is that the kmod RPM has symbols in it that are not in the RedHar/CentOS 6.3 kernels. Because of this the install.sh script fails when it cant apply the kernal mods.
Theres two well known solutions for this problem, 1) Downgrade the Kernal, or 2) install an older CentOS and upgrade it to 6.3 after the integration services are installed.
Theres actually a third option, thats quite a bit easier as well: If you install the RPMs manually and force the dependancy check all seems to be good. A yum update will throw a warning, but the system will still function.
To do this mount the integration services 3.3 disk on your linux instance. Then execute the RPMs directly in the following order:
rpm -Uvh --nodeps kmod-microsoft-hyper-v-rhel63.3-4.20120605.x86_64.rpm
rpm -Uvh --nodeps microsoft-hyper-v-rhel63.3-4.20120605.x86_64.rpm
After a reboot you should be able to use a synthetic NIC, have time sync, etc.