So I've been doing a bit of work to install Snow Leopard as well as iLife and iWork, got to say, not a huge amount of difference from Tiger, so I'm pretty comfortable with all that's before me, there seems to be a fair amount of tweaks but I'm sure I'll get on top of them in due course
As for the installation, all of my files and so on were still available, some bother with 'keychains' and some deleting to do because apps don't work on SL. I've had to reinstall all of my EPSON drivers too.....and the only bit that I can't get to work is QUICKTIME.....I can't find a cheap driver to play AVI files....

......I might have to fork out cash.....

......the movies I have won't play - any suggestions....

.....mobileme account seems to be ok as well, although I need to tweak that a little more
the old domain file for iWeb wouldn't work either, no big deal really, I've just bought a new domain name and busy redesigning my website. So all a bit of a damp squib to be honest, having a bit of fun rethinking that side of things.....
Had a bit of a play with Garageband which looks fun, that'll be my Xmas project.....
so all told, not bad really.......I'm sure there will be more as I do a bit of digging.....