We currently use routable 4507s. We connect to other routers using the interface-vlan IP addresses. I am about to clean up the configuration by assigning ports as "no switchport", then putting the IP address on those physical ports. Is this wise, or even desirable? Is there an advantage either way? Thanks
Without fully understanding your topology this can only be a generic answer.
Given a choice between connecting a router to a L3 switch using a routed port on the L3 switch and a /30 subnet and using a L3 vlan interface on the 4500 i would go with L3 routed ports.
1) If router has more than one connection then with a dynamic routing protocol such as EIGRP or OSPF you can have equal cost routes and virtually instantaneous failover if one of the links goes.
2) You are not extending L2 from the router to the switch which you are with a L3 vlan interface.
As i say this is a very generic answer and there is nothing wrong with using vlan interfaces as the endpoint the on the L3 switch. Given a choice and all things being equal i would go with L3.