I'm in no way in the league of pg or others but I might have an interesting story to share.
While at university I was pretty skint (as students are). Anyway, long story short I happened to "start a company" that never took off but did take the interest of another competitor - who then bought me out (it never came to anything from them - they were "super funded" and had a not-that-good team....).
Anyway; it wasn't a lot of cash considering - but compared to what I was living on...
I immediately went and bought a silly car which ate up petrol and insurance money (tip 1: don't buy a really nice car unless you drive a lot, now I run a 14 year old Peugeot and it is more reliable, economical and fun :)).
This sort of thing (silly spending) went on for about a month until I was stocked up on all sorts of technology porn (in fairness to myself I did splash money on my friends/flatmates quite liberally). I can't exactly remember what made me stop but did eventually realise that I was acting silly ;)
Even when I stopped spending it was hard to avoid buying stuff I saw and trivially wanted - there was no sense of ownership on the expensive items any more (compared to the 32" TV I had bought a few months earlier and saved for for nearly a year) and they never really made me happy.
Long story short; most of it went into Ebay, I put the money into a long term fund and finished up Uni as a poor student.
Two years later the money is still there; I managed to find a job that rocks and pays pretty good (considering). I've got over the need for money/items and have (in my mind) a much nicer outlook on life and "stuff" :)
So, yes, having "large amounts of cash" (relatively speaking) did change me - but not in the way I expected :)
And the best bit is that I have money for a house, wedding ring (hopefully :)), kids etc... in the future if things don't work out.