Here's my One Percent scenario:
I was leery of upgrading to Lion on a late 2006 iMac. Figured Snow Leopard pretty much rocks. But the chief reason is that I use MAME OS X to power an arcade cabinet and was tired of dealing with MAME and ROM compatibility issues.
So I kept my mid-2009 Macbook Pro and the iMac on Snow Leopard.
Just last week, I took the leap to get a new iPad. I've been getting the iCloud itch for quite some time. Figured I needed to get my graphite iMac DV/SE back from its borrower to use that as a dedicated MAME machine, delete a bunch of stuff from my cramped 250-gig 2006 iMac hard drive, then upgrade the iMac and Macbook Pro to Lion so that I would be in synced iCloud bliss.
Well, feel free to call me a Dumb Bunny for failing to avail myself of Lion during its limited availability. This type of circumstance failed to occur to this dumbbuttocks.