Thank you everyone who replied, there have been some interesting ones.
Richard feels that one can only be nostalgic about wood.
Woodcutter/Wouldcutter said that "would" refers to reminiscences either good or bad. I've looked round for a good definition of "reminisce" and related words, but haven't found anything satisfactory so I'll try to define it myself.
One has to remember in order to say what someone used to do so how is that different? We all know the look of someone who is reminiscing - there is an emotional element to it, it's like the person is imagining themselves back in the time and place where something happened and is dwelling on their memories. This is different to relating a plain fact where one would use "used to". I think you're definitely on to sth here!
Metal mentioned irritation. We talk about someone being willful, and "would is the remote form of "will". Maybe this is another one for that long thread - the core meaning of "will".
Lorikeet, I'm sorry, but I think "irritated nostalgia" is an oxymoron. Maybe you mean "irritated reminiscence".
Metal's second post mentioned literary use. Perhaps "would" is slightly old-fashioned too - like the contrast between "ought to" and "should" Some say that "ought to" is slightly old-fashioned.
Thank you Fluffyhamster for the old thread.
Sorry, though, Lolwhites, but whatever else I don't think there words are so synonymous that trying to differentiate them is like guilding the lilly. That might be true for "in spite of" vs "despite", for instance, but I don't think that it is true here.