I think they did it this way so that developers wouldn't have to code yet another resolution for their applications. Unless they find a way to shrink 2048x1536 pixels to a 7.87"x5.3" screen. Images are still sharper on the iPad mini than they are on the iPad 2 since they shrunk 1024x768 to a smaller screen. No it's not retina but that may not be an option, technology wise, yet.
The one thing that I can't stand about Mission Control is that it's a four finger swipe UP to activate vs in Snow Leopard, Exposť is a four finger swipe DOWN to activate. Other than that though, I like it. I haven't seen a difference in Spotlight, though (probably because I only used it to launch apps, and I use Launchpad to do that now ). Though I like how you can Quick Look via Spotlight, now.
I usually use QuickSilver, but I prefer Spotlight from Tiger to all other versions, to be honest XD And then there's the loss of Rosetta... I don't want to be rebooting every time I want to use a PPC application. Also, I'm not a fan of the iOS-like features in Lion
I never really used Hot Corners. The only one I used was the one that puts your Mac to sleep.
I never really got into QuickSilver. I also never really used Tiger. I got my first Mac when 10.5.7 was the current version. The only Power PC app I use is Photoshop CS2 and I don't use that every day so restarting isn't a hassle. Plus, I don't have to worry about quitting anything when I restart because of the resume feature.
I have tons of PPC apps that I DO use, I have Dreamweaver CS, Photoshop 7, an old version of Fireworks MX, that I use more often than would allow such frequent restarting. If they had left Rosetta in it, I'd be fine with it; still probably wouldn't upgrade, but still.
You buy Lion from the Mac App Store on one Mac. Then on the other Macs, you log into the Mac App Store using the same Apple ID you used to buy and download Lion on the first Mac. Then, click on the Purchased tab at the top of the window and next to OS X Lion, there should be a button that says INSTALL. Click that and Mac OS X Lion will download and begin installing at no extra cost. Pay once and you're done!