YES!
Security Benefits of using VLANs
By segregating IP phones into their own VLAN(s), security filters can be implemented in the network to block all unnecessary traffic to or from those devices. This helps prevent disruption due to DoS attacks or attempts to compromise the devices. It also allows locking down access to configuration
and signaling servers to only allow access from phones.
Using VLANs also allows placing IP phones on the public Internet while the connected PCs remain on a corporate intranet; this can facilitate using IPtype services from third parties without the complications of NAT between the phones and the Internet. Since phones have a very limited set of ports required for operation, the additional risk of having them exposed to the Internet can be more easily mitigated.
QoS Benefits of using VLANs
Typically, QoS is used to reduce the packet loss, latency, and jitter (variation in latency) that realtime traffic, such as VoIP, experiences in the network. Packets are marked at the source to indicate that they are real-time traffic, and network devices such as routers and switches can be configured to use that marking (or other factors) to determine which packets need special treatment.
Many network administrators are concerned that devices other than phones will try to abuse QoS policies to achieve better performance. Segregating IP phones into a different VLAN allows the administrator to configure their devices to ignore or un-mark packets coming from non-phone VLANs to defeat these attempts. Some administrators find it easier to base the treatment of packets on the source or destination IP address rather than use packet markings; having phones in particular VLANs makes identifying the IP addresses of phones much easier.
