Regarding unlimited hosted sites, yes that is correct, well officially when your logged in i think it says 999, if i remember right, but of course i cant see anyone using that. I haven't had to use their support yet.
Not much difference as compared to other sites unless you are using some specific mods for your directories where it may become crucial regarding hostgator support, they are good with it just try contacting them and you'll know yes, they allow unlimited sites or directories in their plans.