I'm new to Ubuntu
Well good to see you.
Here's our cutting edge UI that our team have researched the hell out of to bring the user and the computer together in a more harmonious state. You can if you wish change it to something you are more familiar with, but this is our vision of the future, so why not get onboard now.
I'm just upgrading.
Well good to see you're still with us.
Here's the UI you have always used, but I might point out that more options are now available within the bounds of this UI. You might want to read more, or even have a peek at other UI's we make available.
I'm just downgrading
Well I'm really sorry our latest iteration foisted something awful at you.
Here's the system you left behind. We have noted where we think the new system didn't meet your approval and will notify you just as soon as Torvald finishes wringing the necks of those behind your bad experience.
I've jumped from Windows
Well good for you, and welcome aboard.
Here's the ui you're most probably used to, but I'm afraid we won't be able to recreate the same dysfunctional experience that Microsoft designs into its products. You might want to open your computer and randomly rake a fork across the motherboard to recreate the Windows effect.
I've jumped from Apple
We're really sorry to hear you've lost your design job/trust fund/savings.....