I talk to dozens of people every week about what kind of platform best suits THEM for their computing needs. The industry as a whole has made giant leaps to downsize the size and weight of mobile devices and many have done it with a great deal of success. But you're going to need to ask yourself a few questions before you have an answer that fits YOU.
Personally, I'm not a big fan of Netbooks. You mentioned some of the obvious shortcomings like the limited Hard Drive space, minimal RAM. But you're mistaken about those components slowing down your computer. The speed on Netbooks is throttled at the CPU. Most all Netbooks run on an Intel Atom processor. The cheap ones are agonizingly slow. The second thing slowing you down is the Graphics chip. Although Netbooks usually have a sharp picture, it's only because of the limited size of the screen. The cheap ones have terrible graphics processors that use up your small amount of RAM. Finally, Netbooks have no DVD/CD drive. This means that if you want to load new applications on them you have to download them and install them from the desktop (if that option is available). You can always purchase an external DVD drive at a reasonable price, but again we come to the question of how you want to use your device.
You mentioned things like portability, e-reader capable, gaming, internet, video player and music player as items that interested you. If this is the case, you might consider an I-Pad. You can do all of these things on an I-pad and they're coming out with different apps every day. I don't own one, but for simple mobile functions like you're talking about it looks like a good bet.
There are also lots of smaller, lighter knee-tops (small form factor) coming out but once again, most of them don't have built-in DVD drives. But heck, everything will be wireless in 5 years, including all of your apps. Microsoft provides most of their Office apps right on line (in the cloud). Over the next year, I expect to see a lot of movement in this ultra-lightweight laptop market.
Finally, like most of us our budget is a factor too. You can fork out $1,500 for a Macbook Air, $880 for a top of the line I-Pad, or as little as $250.00 for a cheap Netbook. It seems like in this world, when you get more - you can expect to pay more. I've seen $500.00 Netbooks with all of the bells and whistles that run Windows 7 without a hitch.
Bottom line for this old timer is; I'm going to wait another year to see how this new market irons out. This goes for the new line of BIG SCREEN TVs too. It's beyond my imagination how you can shop for a 55" TV with 1080p, and the prices range from $500.00 to $3,500.00. Yikes!!!
I expect that between the Spring - Fall of next year, there are going to be a lot of nice deals in this ultra-portable market.