1. He's right about the compatibility issue. Most programs would
run correct when select to run in compatibility, but not all.
2. Whole load of crap. As far as networking is concerned, it's the
way you tweak your PC. Also, if you are thinking of sharing files
within your own local area network, be prepared to troubleshoot.
Vista and other operating systems don't share files real
well.
3. Virus issue isn't as common as XP, but doesn't mean there's
none. As Vista is getting popular, you will get to see more viruses
for Vista.
4. Don't get him to install XP for you. Since he has the
"no-need-buy" version of Vista, chances are he will have the same
version for XP as well. You could jolly well run into problems with
Microsoft as well if he installs for you. Get your own XP
disc.
Also, you aren't allowed to use your friend's disc to install Vista
Ultimate, it's against the laws. If you want, you have to buy your
own copy.
5. If your common list of Vista-compatible programs include games,
then be prepared that the list is quite small.
In summary, if you are adventurous, go for it. If you aren't, stick
to XP or older versions of Windows.
Better still, get an Apple or Linux.