Hi Rob,
Remember I said me and my brother had bought Desires? Well we have gave them to our girlfriends and bought Samsung Galaxy S.
He works in CPW and so I got a third off and went sim free. Cost me £315
Well first off, it does not feel in the hand as good as the desire. Hard to expain really just the desire has a weighty compact quality feel to it and I don't have the awesome litttle weather widget anymore and cant find one as good lol.
However the screen is amazing and I can view it perfectly without the backlight (still really bright and I just realised I don't even use it with the backlight on), outdoors/close to lots of bright natural light like windows it is noticeably better than the desire.
I can text way easier on it and the video camcorder is ace (720p is why the iphone was so tempting to me

).
I have read people saying they think the phone is ugly but having had both in real life I much prefer it to the desire and its rubberish with plastic browness!
Here is a little vid my brother did of our younger brother
http://www.youtube.com/watch?v=iwFa0FiSX8s Looked better before the upload but still it looks pretty good for a phone
I never really got on with the desire but do really like the galaxy s. There is lots of little advantages
720p recording
Better still camera pics
Wireless n
8gig internal (sim free) 16 for voda
Bigger screen with super amoled screen
Battery last longer
Typing is much better and so is the general usability, could be the software or the bigger screen can't say for sure
faster framerate with games I have tried like raging thunder 2
the samsung facebook is much better
the sound quality of the loud speaker seems much better
the headphones are much better and I really do believe the actually sound coming out of it is better too (could just be placebo)
um just lots of little things but I just did not get attached to the desire and if I was I would just hang on to the desire and upgrade to the next really big thing and not just a load of little improvements
Cheers