The netbook style of laptop is hot right now. Really hot. A big reason for this is because the price for them is really cheap (even as low as $250 brand new or $299 for the Dell Inspiron Mini 9), so yes, they’re flying off the shelves as fast as manufacturers can make them.
However as a far as it would suit as a primary computer replacement, the answer for most people would be a flat-out “No.”
Even though I personally champion the netbook format, I won’t say you should use it as your primary computer.
A few truths about netbooks:
They are slower than standard-sized laptops. You’re not going to see any blazing-fast performance out of one of these things. It’s not terribly slow, but it is noticeable.
The keyboards are physically smaller. Got big hands and/or big fingers? Then you’d hate the netbook.
No optical drive. I personally wouldn’t miss this, but a lot of people would.
Small storage. Netbooks come with storage as small as 4GB. Others (like the Dell Inspiron Mini 9) do come with 40GB and up for storage. But for some people this simply isn’t enough space.
Forced with XP if using Windows. If you want a netbook with Windows, it must be XP. Vista requires more horsepower than a netbook can provide, therefore it isn’t available for it (but this may change with Windows 7).
Even though Linux is better (and cheaper), most people won’t go for it. Since day one, netbooks have been offered with a Linux distro as their primary OS offering. It works very well and it’s quite speedy. It’s always cheaper than Windows concerning the final price of the unit (by as much as $100 cheaper in some instances). However there are many that see Linux as a turn-off and aren’t willing to pay the extra “tax” for Windows – and furthermore don’t want to flip out extra just for XP.
What are you paying for with a netbook?
You’re paying for portability. If you want a laptop that’s under 3 pounds, has a reasonably good screen, does basic tasks (web browsing, office apps, etc.) and can basically go anywhere, the netbook rules the school in that department.
However if you expected some blazing-fast desktop replacement, the netbook is definitely not it.
Using myself as an example:
Either this year or next year I’m seriously considering picking up one of these things. What I would primarily use it for is blogging via Windows Live Writer, my office-app stuff, email, instant messaging and not much else to be honest. This is mainly due to the reason I know it’s not capable of much else – and that’s okay. What I want is a cheap portable computer – and the netbook suits.
But this doesn’t mean for one second I’m going to throw out my big-box PC because there’s absolutely no way I could do proper video editing on a netbook.

RE Netbooks and if it’s Windows it has to be XP:
This reply is written on a Netbook that came with Vista, and there is nothing wrong with the performance !
I stand corrected. What make/model?
HP 2133 (Vista Business)
http://www.ebuyer.com/product/145007
I bought a joybook lite from Benq in hong kong while on my current adventure travelling around the world, its small and strong compact, 3 USB ports so dont need an optical drive and when home if using it in place of a desktop you can plug in a USB external optical drive no issue, it runs pretty fast with a 1.6ghz processor, i prefer windows XP to vista anyday anyway so no issues with the OS. the hard drive is 160gb SATA (which may be more delicate than the SSDs but i like the bigger capacity. The keyboard is actually 90% of full size which for me is why i picked that particular one. so far on travels its been an awesome tool to have. wifi is more places than you think in the world.
My Aspire One came with Linpus Lite (which I hate with a passion !)I’ve since tried a few other distros, but have finally settled for a Vlite Vista home basic and the Black Viper settings.
I’m also beta testing Windows 7, but to be honest I will most likely stay with Vista Basic (on the netbook at any rate !)
I am running W7 on a Netbook, and this works pretty well. Admittedly the machine has 2Gb memory (upgraded from 1Gb), but it can host a 1Gb virtual PC even, in which I can run XP. Shame that the latest version of Virtual PC (for W7) requires the PC to have ‘Hardware Virtualization’ features. It would be much more sensible if MS changed that to be an option, so that many more machines can run the latest version.