The experience included something I have never seen before with any system I've used in my long computing career - an upgrade that resulted in more free space on the hard drive than there was before the update. This has been widely reported over the past few months, but seeing it for yourself is something else again.
My Mac is a two year-old Mac mini with an 80GB hard drive that came with Mac OS X 10.5 (Leopard). Prior to the update, it reported 35GB free out of roughly 76GB available. After installing the upgrade it reported 46GB free and after subsequent online updates, which themselves involved about 700MB of downloads, it reported 47GB of free space.
For a Mac like mine with relatively little storage, this is a huge bump. I gained 12GB or 15% of the total drive!