in my experience it's not that good, unless you have lots of iskies with you. basic modules might be ok, but the somewhat better modules are hard to come by (expensive or not available at all). rats drop lot of the same modules (hybrid guns, (remote) armor repair, and some other tidbits). dont know about mission npcs though.
what i do is jump over to my empire JC now and then and do some shopping. we're lucky that Rub is willing to make regular trips back and forth with his carrier or rorq
Rubs trips also carry regular batches of BPCs of various stuff, so ships & ammo isnt so big a prob