There are currently three classes of laptops: Atom, Celeron/Pentium and Ultrabooks.
Like this ASUS X205, they usually use the Intel Bay Trail Z3735 CPU with 2GB RAM and 32GB or 64GB solid storage. Yes, they are powerful enough for your daily work and entertainment and they are fanless, I have been using one (the Lenovo Miix) for a year now as my only computer. You can easily add more storage with a 64GB SD card for about $25. This ASUS looks and feels very good - thin and light, and unlike all other ugly ASUS, the frame is elegantly thin and matte. While the screen is sharp, clear, bright and contrasty, the up/down view angle is narrow (the left/right is wide) and color is cold (dark-blueish). These two things, narrow view angle and cold color, are pretty much the only imperfections about this perfect laptop ever.
There is a fast version of Atom, the Z3775, which is used in the ASUS T100. It is clocked higher to be as fast as Celeron and Pentium.
Celeron and Pentium laptops (2-in-1):
They are basically Bay Trail clocked at higher frequencies for increased speed. Celerons (such as N2830) are dual core while Pentiums (such as N2930, N3530) are quad core. Not all of them feature the Intel Quick Sync technology found in Atom Bay Trail for real-time superb video compression. This is a very good thing to have if you ever need to convert a video from one format to another or to reduce its size for sharing. Usually N##20 (e.g. N3520) do not have it while N##30 (e.g. N2930, N3530) have it.
For example, this Lenovo 2-in-1 selling in BestBuy has an old N3520 CPU and therefore you'd better not buy it due to lack of QuickSync:
The Toshiba Radius found in BestBuy and the Dell 3000 found in CostCo and everywhere are very similar to the Lenovo 2-in-1 but both have QuickSync. The Toshiba has a Celeron N2830 while the Dell may come with either a Celeron N2930 or Pentium N3530.
These Celeron and Pentium 2-in-1 laptops usually come with 4GB RAM and 500GB HDD, adequate for everyone. You may add more RAM. You may also replace the slow HDD with a SSD for much better performance for very little money. They run 64 bit Windows which is far more reliable than the 32 bit on Atom laptops/tablets, due to absolute enforcement on driver signature.
All the sales men in stores will push these expensive craps to you. They are rip off without any premium stuff in and out, stay away from them unless you see one below $500. If you are willing to pay a premium, then get the Apple Macbook Pro 13" with retina screen. The touchpad alone is worth the money. Yes, Apple touchpad is that good, go give it a try in BestBuy with your two fingers scrolling down and up within a web browser. If you need Windows, then install Windows on it. The cheapest configuration is enough for everybody, any higher options are totally more rip off. It is thin and light, no longer need to bother with any Macbook Air.
If you need 13" and do not want to spend a thousand on a common tool, then take a look at the HP Stream 13.