We have a couple of different systems. The biggest pro and thing they all have in common is that they work WAY better than anything BMD has offered to date.
The base system is a two-wire party line by RTS. A central power unit (PS10 or PS31) connects to many user belt packs via standard XLR cable. The belt packs (BP325) offer two channels of communication, and use widely available headsets (BeyerDynamic DT108, DT109 to name 2) with multipin XLR connections (4pin or 5 pin male xlr). They crank enough headphone volume for outdoor motorsports/concerts. Dual ear and noise isolation headsets (David Clark headsets) are easily added when needed, or go with a lightweight headset (Telex PH88) if thats your thing.
Our bigger system use a matrix intercom, the Zeus or Zeus3 also by RTS. This multiport (24 or 32) 4-wire base has MANY options to expand or upgrade. The rack mount stations (KP12, KP32, expansion panels) can have upwards of 32 talk/listen keys, each key infinitely programable to be a single talk path, or to multiple users. It can interface with the party line system above, telephone, internet, IFB, radio systems...well just about anything. We also have added Dante networked audio to many of the ports, and now use Dante belt packs for com/ifb simply by plugging the belt packs into a managed POE network switch, even remotely connected by fiber miles away.
All of the above have been integrated into our production systems, so that cam/audio/coms connections are all available in one remote fiber connected box. Deploy a box anywhere you want to work. A short harness from this box is all that's required to make a camera position fully functional.
The only con I can come up with is maybe price. A fully loaded Zeus system could easily run past $10k+. In terms of flexibility and ease of use tho this type of system has no equal. Giving your director a single panel/headset that can talk to multiple discrete systems is THE way the big boys do it.
You don't need to break the bank to have any of this. Components to RTS and Clearcom (another great com ecosystem) are available in the used market for a fraction of what new gear costs. Most times they work well-it's difficult to break these things. The headsets are the only thing I'd prob buy new in that case...
I'm always happy to help anyone out with shopping a complete system together