L2TP LAC is a feature that will come in handy to anyone deploying PPPoE on their network and we're currently stuck using Cisco for this. Mikrotik already supports the other half of this type of setup, LNS and it's my hope that we'll finally be able to replace the remaining Cisco routers in our network with Mikrotik when Mikrotik adds this feature to v7.
For those who don't know about this feature, when configured an L2TP LAC will accept a PPPoE connection and immediately turn it into an L2TP tunnel to another router. This has a few advantages, the main one (To me) is that the L2 PPPoE connection can be handled by a router close to the customer, but then the session is immediately turned into a L3 tunnel to a router across your dynamically routed network, or potentially the internet. The LNS router will then accept the L2TP tunnel and handle assigning it an IP and routing it the rest of the way. In a current Mikrotik network, the only way to send a PPPoE connection to be handled by another router is by using things like MPLS/VPLS or EoIP, which add a lot of complexity that you may not need.
On a Cisco setup, this feature also allows you to do a bit of redundancy/load balancing, which can sometimes be a bit of a challenge on traditional PPPoE setups. It allows us to pick multiple IPs to round-robin load balance the sessions to. Alternatively, you can choose the backup destination in case the main L2TP LNSes aren't responding.
One big use of L2TP LAC on our network is being able to offer other ISPs wholesale access on our network. You can configure the realm/domain in the PPPoE username to forward the L2TP tunnel to different routers. So your customers could have a PPPoE username of "email@example.com", which on login the LAC will send the L2TP tunnel to your LNS router, but when a the other ISP's customer "firstname.lastname@example.org" connects with PPPoE, your LAC can send it to the LNS router at the other ISP to be authenticated, have an IP assigned, ect.
Right now there literally isn't an option for a router with this feature if you need it to be compact and low power consumption, it's a feature reserved for high end Cisco/Juniper routers despite seemingly being a pretty straight forward feature.