It has a start menu including aspects of the W7 list style and tiles of W8.
You'll want to delete some stuff there ad add some of your own most used items.
Otherwise everything seems pretty much where you'd expect, and after a few days you'll not even think about it.
I found significant increases in speed to open programs.
Most if not all programs will behave and look much as before.

The actual update/install will take about an hour after it's downloaded.
You can just leave it for a good while during this, but towards the end you need to go through some basic questions to do with how it runs behind scenes.
Don't rush this, read it properly and go into advanced options as one or two things might need changing though you can switch them later if you remember