Darwin, and my other birds, are fully flighted. I personally wouldn't take away their natural ability to fly. Darwin is very bonded to me and allows me to carry him most places, but sometimes when he is on my chair in my room and I move to the bed, he will fly over to me. I have no problem with him flying to me since it's his choice. Sometimes he doesn't fly to me so it's up to him. I do, however; have to take precautions just like everyone else with flighted birds. I always keep the doors locked so no one walks in, I have showed Darwin all of the windows and mirrors in the house (they all have blinds and curtains too), I keep the toilet seat closed, I make sure there are no open chemicals or things he can get into (just tonight he tried to take off with one of my pencils so now I have another thing on my list of things I didn't realize he could get to before!

), etc. Bottom line, as it has been said thousands of times before, to trim or not to trim is a personal decision, but mine is based on my ability to keep Darwin and my other birds safe, and their natural need (and love I think

) to fly.
In regards to the plucking, I don't think there is any information/research out there that supports the idea that flighted birds pluck less, but who knows, it might. Darwin has no behavioural "problems" so I really can't say how being flighted has altered his behaviour, personality, etc. I think, in general, allowing animals in captivity to be able to express their species-specific behaviours (such as flying in birds) does improve their mental, physical, and physiological well-being and has been extensively researched with many mammals in captivity...not so much with birds as of yet. But it makes sense that birds, not being domestic animals, and being more closely related to their wild counterparts, would fall into this same thinking.