First Contact missions are fun. They all run about the same, but it's much less time consuming than the diplomatic investigations, well some of them anyway. I did a first contact mission yesterday that was really funny. One of the representatives made a joke about our starships running on matter/anti-matter propulsion. He said "oh yes, let's build our ships around a big bomb! Great idea! I bet your ancestors used nuclear propulsion too didn't they!" Just thought I would share that story.
The diplomatic immunity thing is fun too. Omega Leonis (Klingon space) is the place to go for rare Doff missions. You'll get some there that will unlock strings of missions with nice rewards. I'm trying to work through a facility 4208 string right now that gives some good rewards. This commendation xp boost should help matters!