Some caveats:
1. only the ME version supports MPLS, in case you want to overlay an MPLS TE/VPN network on a Metro Ethernet Forum (MEF) ELAN raw Ethernet service. 2. If you are using IP multicast, make sure that the Metro Ethernet provider supports PIM snooping, otherwise (S,G) directed multicast packets will be flooded out all service provider ports that connect to your devices, emulating a 1993-style Ethernet hub.
3. Only "switch-style" QoS, not full-blown MQC. The 3750ME has two "router" ports which do mostly support MQC, but still have some limitations (e.g. traffic locally sourced from the device is not correctly classified / marked). Which is all kind of what you'd expect from a switch, but may be relevent if the original question was "which router?" Regards, Tim.