I use Ubuntu and find it to be very good. I very rarely find the need to use the kids Windows PC these days - have everything I need (including Open Office, Firefox browser and Thunderbird eMail) on my Ubuntu PC.
When I first installed Ubuntu they were on the "Dapper Drake" release which definitely came as a Live CD. I'm on "Edgy Edge" now and will upgrade to "Feisty Fawn" over the weekend. Not sure whether they've dropped the Live CD now - but if you burn it to a CD and reboot it will quickly become clear!
RC