Spent a huge amount of time researching and using the pre-Ultrabooks (like Samsung Series 9) and then the first Ultrabooks late last year. Eventually returned all those and bought the light, small, powerful, expandable, reliable IBM ThinkPad X220 instead. That being said, I use my iPad 3 more than the ThinkPad now though (for personal and travel use)...

An excellent site to look at is Ultrabook News. Check out the Home, Ultrabook Comparison, Ultrabook Reviews tabs.

Samsung has great products and IBM (and others) are coming out with new models that will work even better with Windows 8.

MacBooks, although not my device of choice, are excellent in this market. I found that I could not get into the Mac OS and that running Windows on a Mac is a poor option (if you are primarily a Windows app person).