Most Netbooks do indeed have the same or very similar spec when it comes to RAM, CPU and hard disk. The main things that differ are the screen size (8.9" to 10.2"), speakers and the battery life. For example, the Acer Aspire One and Samsung N120 have the same Atom N270 CPU, 160GB HDD and 1GB RAM, but the Samsung N120 has better speakers, larger screen (10.2" vs 8.9"), much longer battery life (up to 9Hr vs 3Hr) and a larger keyboard.
One thing in common with most Netbooks is that they run Windows XP and the performance feels a lot better than many entry level laptops running Windows Vista, at least every one I’ve used. For example, my Samsung N120 fully boots from the power button to the desktop with HDD activity stopped in 50 seconds. Generally I put it in hibernate, in which case it is ready to use in a couple of seconds, much like a full size laptop getting out of hibernation. From my experience, most applications run just as smooth as on a full size laptop, obviously except anything CPU or memory intensive, such as a graphics suite, video editor, etc. For video, it plays pretty much everything including H.264 up to 1280x720 with smooth video.
As the Atom CPUs used in Netbooks are quite limited, if you do get one, be very careful which software you install that loads on startup or which runs in the background. For example, Skype is quite hefty and can add around 25 seconds to the boot-time alone! A workaround is to configure each software to not automatically start with Windows and this way you can manually run the software as you need it.
I would not worry too much about hard disk space, as 160GB can hold quite a lot. Just don’t dump your entire movie collection on it! If you need additional storage, get a 2.5" HDD, which is self-powered by USB. An external Western Digital 500GB passport is about half the size of DVD holder.
The screen will take a little while to get use to due to its lower resolution. Despite the myth that the writing will be tiny, I find it very comfortable to read the text on my Samsung 10.2" netbook. However, after using an Aspire One with an 8.9" screen, I do find the writing on its display a little too small for my comfort. The resolution of nearly all Netbooks (8.9" to 10.2") is 1024x600, which is the same horizontal resolution of 15" PC LCD monitors, so the vast majority of websites display fine on it without the need to scroll left/right. Due to the narrower height, it’s best to avoid installing toolbars. The best browser from my experience on a netbook is Google Chrome, where the header contains nothing more than the tabs in the title bar and the address bar below it, leaving plenty of viewing area for displaying webpages, probably as much vertical viewing area as using Firefox without toolbars on a regular 1280x768 laptop display.
For travelling, especially on holidays, a Netbook is a lot more travel friendly. As they are around 1.5kg lighter than full size laptops, this is a huge weight reduction in a carry-bag, especially in an airport. It’s also more comfortable to use on a bus or plane and the lengthy battery of some (e.g. my Samsung N120) means that it will run most of the day. At home, I occasionally use mine as a portable TV, using DVBViewer to stream satellite TV from my desktop.
The following shows a rough size comparison between a 15.4" laptop and a 10.2" netbook when placed on top of each other:
Despite the size difference, the distance between the left of the ‘A’ key and the right of the ‘;’ key of my desktop PC keyboard is about 18.5cm. The same measurement on Samsung N120 is also about 18.5cm! The main keys made smaller are the 2 far-right keys on each row.
The following gives an idea of how the viewing width compares between the two while on the forum index. This also gives an idea of how much smaller the the writing size is, since the forum has a fixed width: