Lion high CPU usage

I just bought my first Mac (MacBook Air 11") on June and used without any problems until I upgraded to Lion one month later.

Since the upgrade the CPU usage has been a real pain. After using my MacBook for about 30 minutes or so the CPU usage by Finder alone and many times along with some other program (I've seen with Thunderbird, Excel, HyperEdit and Firefox - no flash, just with Google main page open) shoots through the roof, the result is a sluggish & hot computer and a battery killer.

This has been real disappointment for me coming from a Mac... Please, anybody has any thoughts? BTW, I already tried to delete com.apple.finder.plist with no result.

Any help will be greatly appreciated, thanks!

Here are some links with pictures of my Activity Monitor:

Finder + Excel without any spreadsheets open
http://img828.imageshack.us/img828/4200/finderexc.png


Finder alone
http://img199.imageshack.us/img199/1136/finderl.png

After 3 weeks trying to find an answer w/o sucess finally found the solution: Go Back to Snow Leopard.

I would not recommend anyone to upgrade yet.