There are two things that prevent netbooks from serving as your "primary computer." The first is size; the second is performance.
The problem with netbooks is that they only fit in as secondary PCs. That might be fine for many enthusiasts, the added benefit of mobility is mitigated somewhat by the headaches of maintaining synchronized data and modest performance potential. Fortunately, that performance issue will be addressed in the weeks to come as AMD's 18 W Zacate and 9 W Ontario APUs start finding themselves in netbooks.
The size problem is never going to go away. You can't make a 10.1" screen bigger, and at 10.1", it's hard to change the fact that you're using a screen barely larger than a mousepad and a miniature-sized keyboard. The next best thing is an upgrade to a 12.1" screen, which offers some much-needed additional real estate.
All things considered, 12.1" is a great compromise, considering that it gives you about 44% more display space and provides the benefit of a full-sized keyboard. The downside is that you are still stuck with what many consider an underpowered form factor, particularly as it relates to multimedia.
When it comes to word processing and more general-purpose use, you should be fine. However, something as simple as 1080p H.264 playback brings the current crop of CULV notebooks to the edge of their performance ceilings. To top it off, you can't expect to play games on any current netbook. The CULV notebooks shown here don't fare much better, even if World of Warcraft can be dialed way down and made somewhat fluid. It's just unfortunate that we can't turn the settings any higher to enjoy what the game really should look like. This isn't going to change until we get to see Brazos-based notebooks hit retail shelves.
We have been told by our system vendor contacts that we should see Intel Core 2-based CULV notebooks around at least until Q1'11. Asus currently has a small handful of CULV notebooks based the ultra-low-voltage Core 2 processors, such as the UL20A, UL30A, and UL80VT. The 10 W ULV Core 2 processors like the SU7300 offer significant power savings over the 25 W Penryn-based chips, which makes them ideal candidates for CULV notebooks. It is still possible to get a thin-and-light notebook with a Penryn-based Core 2 Duo, but the more powerful part comes with a higher price tag, as other components like denser batteries are also required. Priced at ~$590, CULV notebooks like the UL20A are still more attractive from a budget standpoint, even against some of the newer ultra-low-voltage Arrandale-based notebooks that run ~$699.
If you are shopping for a "single computer" that can make your life simpler, CULV notebooks are where it is at. However, we have a warning. We are potentially at the cusp of a horsepower breakthrough with Brazos. We've already seen how the platform behaves on the desktop, and it's actually competitive against Intel's ULV Celeron SU2300. The real difference is that it's massively less expensive. This should translate into some respectably-performing mobile systems at very attractive price points. They're not ready yet, but they should be soon.
If you can't wait, we recommend something along the lines of Asus' 1215N. The Ion 2 and Optimus technology combination is good for power consumption. And the Core 2-based ultra-low-voltage processor delivers quite a bit of performance given its power profile. As capable as AMD's Nile platform was, it still used more power than it should have in order to fit in well here. Our suspend benchmark shows that. Until Brazos hits the shelves in netbook/notebook form, Optimus/Ion 2 and Core 2 Duo CULVs are still a solid bet.