This is another flip-flop for me. On one hand, I use iTunes for most of my media.
On the other, I love watching movies and being able to control them with the remote via Front Row. Even more-so, I love the ability to easily browse new movie trailers. Another feature of the Mac OS I'm sad to see go.
Maybe Lion really isn't for me.
Fortunately for you, XBMC and Plex more than covers those bases.
Ya I'm on the fence - that's assuming my ancient Core 2 Duo iMac will even run it. If I can install it Lion will be my last OS X install - I refuse to buy a new system until Apple offers a non-glossy screen option. They refuse to do that, so I refuse to ever buy another Mac.
Sigh.
Your iMac has Core 2 Duo. That means it will run Lion just fine.
For non-glossy screens: Apple's laptops offer them. Desktop? Just get a Mac mini and an external display from another manufacturer. Problem solved.