Undoubtedly, netbooks are very portable and with long battery time. However, its much slower Atom CPU and the entry level Windows 7 Starter makes it unusable in many situations.
Take for example the latest Atom N550, its CPU benchmark is just around 564, just 1/3 to ¼ of the performance of a low end Core i3 CPU. Actual hands-on experience reveals if you have web browser, Outlook, Excel and antivirus running at the same time, please have some patience.
Windows 7 Starter is never my choice. In practical use, it is worse than Windows XP Home. Maximum RAM support for Starter is just 2GB. No multiple monitors, nor remote desktop host support, … too bad! Even when I tried to configure an IIS on it, failed as it's not supported! I've to switch to use Apache.
In conclusion, netbooks are good for simple, light weight processing application use, such as browsing web pages, checking emails and simple document editing. However, for serious business use or some processing speed demanding applications, they're never your options.