So i can take an RB750, run a wan connection into port 1, run a hotspot off of port 2 (with its own DHCP server) and a totally separate network (with another DHCP server) off ports 3, 4, and 5?

Yes.

http://wiki.mikrotik.com/wiki/How_to_co ... ome_router

That final config more or less applies to what you're doing - just instead of using one interface for a DMZ you'll be using it for a Hotspot.

So there was a trick to accomplishing what I wanted... I had to set the "master" to none on the ports I wanted to setup with a different ip / dhcpd server etc. now that I have figured that out I love these things!