I have been a home Mac user for about 10 or 11 years now, and using one for work for 3 or 4 years.
That's more than enough time to understand that Apple's upgrades are sometimes about forced obsolescence rather than new features. My iMac - barely 6 years old and running like greased lightning on Snow Leopard - can't run Lion because its processor is one generation too old.
That appears to be an arbitrary decision on Apple's part, as a number of Lion beta testers managed to hack Lion into working perfectly well on Core Duo hardware, simply by removing a single file whose purpose was to do nothing more than check what processor was on board.
Lion may turn out to be more features for less money than earlier announcements suggested, but for me, it's going to cost a smeg-load more than £20.99. As I, like you, swap constantly between Mail and Calendar on the Mac and an iPad, via the soon-to-be-defunct MobileMe, and because I need to run Lion on the Mac after next June if I want to maintain both that functionality and my me.com email addresses, via it's successor, iCloud, I am going to have to invest in new hardware.
I wouldn't bother, but as we took the decision to build the bookings system for our B&B around the Mac's calendar and have invested in advertising with a me.com emai address, we have little choice.
At the moment, I find the mere mention of Lion rather irritating.