It was the easiest install of an OS ever.
I do recommend installing any other software updates before downloading Lion. Go to the main Apple menu (top left) and select software updates. I had them pending for three programs including iTunes. Then go to the Apps Store and you will likely see updates there for applications you bought from there.
Then download Lion. Took barely 20 minutes for the 4GB file to come over on my wireless Verizon FIOS connection. After a reboot, it took about 30 minutes for the OS to install and about another hour for everything else to fall into place (i.e. the Spotlight indexing all my files).
The only glitch was when I opened iTunes, for some reason, the library wasn't updated properly so I had to download a patch (just follow the prompts) - took only a few minutes and it was back to normal.
I'm a fairly new Apple user and I must say that the whole experience has been much better than Microsoft so far.
Same here, upgraded last night with no problems.