question

Just check latency in your office.  If you are consistently under 40 ms then you will be fine.  The good is that the service seems to be consistent (I'm only 2 months in).  The bad for me (not for you though) is that my users are not under 1 roof (85 of them) and we have legal outbound Caller ID requirements.  Because RC is only able to display 1 name on every account we had to setup multiple accounts just to accommodate that need.  They can display any number virtual number though.  They also don't have a means to do certain bulk administrative tasks.  However, the features are solid, and because you are at 75 users you will get US-based customer service (if that matters to you).  Although they would like for you to use their phones we are not. We are using Grandstream phones.  I would suggest thorough testing before committing the whole load nonetheless.  Some issues they seem incapable of resolving in a timely manner.  I've come to find out that their higher level tech support is not in-house.  It hasn't been an issue, but it seems they farmed out the infrastructure build-out so the real issues have no way of getting hashed out quickly.  Again, hasn't been a problem, but just giving my honest assessment.