shurik1973,
It looks like Luke hasn't given an answer, but I'd be happy to present the way Lion enhanced my Mac experience. Personally, I think it's the most significant upgrade since Spotlight appeared.
1. Instant contextual definitions. I could only do this with difficulty on select applications, but now it's universal. In seconds, you can get definitions, synonyms, etc. as a part of the system. No more having to use a widget or application.
2. Reading list for access to links. I usually juggle several sites and questions (like the Apple Support Forums), and Reading List keeps them all in one place, on the desktop. A nice feature, very easy to use.
3. Safari navigation. Every session, on Safari, using gestures like a two-finger swipe immediately moves you to the previous screen. Or three fingers to access all active processes at once. I use this constantly.
4. Drop Copy. I have a MBP and iMac, and Drop Copy lets me share files instantly without having to use USB sticks or email. Really easy, and intuitive.
5. Preview hasa new dimension. Now, I can view documents in a smaller preview window to remind me what the content of a file is, regardless of the application. I don't use Preview a lot, but the information I get is right on target.
I'm still learning how to use Lion, and certainly there are some features that will be tweaked over time. And others, I probably won't use. But for me, Lion's features are very significant.