1) online will come pre-installed (more than likely)
2) from apple shop - you will get drop in DVD until stock runs out
3) from Authorised seller - no disk - but you log onto apple.com and request a DVD at a small cost after authenticating your system
We use John Lewis for (most) Electronic purchases in the UK because of extended warranties and no quibbles, even though apple have opened a new store in Kingston Upon Thames and have a modest range - play at Apple buy at John Lewis, money goes to Apple no big deal !!
Yesterday I picked up 2.4ghz 20" iMac and got the DVD online.
Important : Apple store guy said the DVD was same as normal Leopard DVD, I enquired in future do we have to re-install 10.4 and 10.5 on top? First answer was no, but when I pushed the guy asked a Genius, whose answer was YES, as iLife had to be there first. Not the correct answer as Mactari and others have proved otherwise on this forum you can load apps from 10.4 after 10.5 install.... thanks guys.