Size. If there is something I like is to be able to use the iPad practically anywhere. I am writing this on a plane where it would be hard to fit a laptop, given their "fit as much people on an aircraft as possible" policies. The iPad fits nicely and allows me to get the job done. It is very portable and you do not even need to take it out on security controls.
Screen. Colors are vivid, resolution is nice and the overall usage of the screen is a joy. At 768x1024 pixels games look great, but almost all other applications can benefit from the screen too. Sketches 2 has even more potential here than on the iPhone given the screen real estate.
Sound. Due to its thin size, I was not expecting to get good quality sound. I am glad I was wrong. For my ears, the speaker on the iPad is practically of the same quality of those on my 2007 Macbook Pro.
No heat, no noise. On most laptops, and computers in general, CPU or graphic intensive applications cause the temperature to raise. In the case of laptops on your lap, it can get uncomfortable. But it is not only that, raising temperatures imply heat dissipation mechanisms, which are normally noisy. Not with the iPad. Even while playing games, the iPad is cool and quiet.
Battery life. You can play games, watch videos, listen to music, browse the Internet or whatever you like to do. The battery will last for at least 6-7 hours. In my experience, it can even surpass the 10 hours of the Apple specifications. Amazing.
Instant on. Casual use feature never one. No waiting for your computer to boot up. Want to google something? Grab the iPad fire Safari and surf away. Look up an article on Wikipedia? Play a game? Same thing.
Safari. If there is a killer app that comes already installed in this device, I would say that is Safari. Browsing the Internet with this is a joy. It was not long ago that many Internet sites read "this site looks great at 1024x768". Here you have it in the palm of your hands.
Memory. The iPad has 256Mb of RAM, the same as the iPhone 3GS. I find this the weakest point of the iPad. Checking the crash logs, running out of memory is the primary cause for most of them. Having much higher resolution than the iPhone, this is not strange. I would have guessed that Apple had placed at least 512. Maybe on the next version.
Weight. Obviously, at 1.5 pounds (680 grams), it is much lighter than a laptop. However this machine is supposed to be easily held with your hands. Reading a book or playing a game can easily get tiring given the heaviness of the device.
Battery charging. If you connect your iPad to your computer it will take a while to get it charged. In my tests 5 hours did not get me a full charge. Fortunately, the charger included with the iPad, even with the same size and aspect of those of iPhone and iPod, is more powerful, so it is able to speed the charging process. Still long.
No protection included. With such a big screen, the iPad can easily get harmed if unprotected while traveling or if handled carelessly. A simple cover to protect the screen would have sufficed to keeping the screen safe in most situations.
Screen becomes dirty. Oleophobic or not, the screen easily gets full of fingerprints. This is not much of a problem while working with the device, but does not look good when the screen is off.
iPhone Apps. I am glad that I can run iPhone apps on my iPad, don't get me wrong, but they do not look good. At 1x apps look too small, at 2x they look pixelated. I believe we could see a better 2x mode in the future.
Mail app. While email look good, navigating between accounts takes several steps. In addition, there is no mail list while reading your mail in portrait until you hit the email list. Then, there comes a popover, you select a new message, the popover goes, and you have to repeat this process again. Personally, I want to be able to switch messages and accounts quickly independently of the device orientation.
Overall the iPad is an amazing machine, more taking into account that this is version 1.0. These are just some of the small things I would like for Apple to improve. However, I must say that I am very happy with it both as a user and as a developer.
Written on an iPad, using Pages.