I like network manager, personally, but I don't think it's going to offer much of a improvement over 'post-up' calls.
Generally what you'd want to do for network-manager is to put your scripts into /etc/NetworkManager/dispatcher.d in the typical "if [ "$2" = "up" ]; then" style format.
To get the best benefits out of NetworkManager you want to disable all the 'legacy' configuration plugins and use keyfile. That way you can edit all your network configurations using a 'ini' file format in /etc/NetworkManager/system-connections/
The advantage to this is that you can support a much more diverse amount of network connection types with better granularity then you can through traditional distro-specific configs.