"Not the first tablet, but the first that matters."4.0 starson by mpias
Pros: Great form factor, lots of available software, elegant OS, good battery life, excellent display.
Cons: Lack of Flash, no camera, cumbersome file transfers.
Summary: There have been tablet computers prior to this, it's just that none were designed well enough to be commercially successful.
The iPad really is an impressive device. The iPhone OS translates beautifully to the larger format. The vast majority of my iPhone apps work fine on the iPad. Though apps designed for the larger screen are much more pleasant to use, that doesn't detract from the functionality of the older apps. While it isn't designed to replace a computer, I find that I'm using it a lot more than my laptop (I stopped using a desktop computer a few years ago).
Surfing the web just works really well with the touch based interface. The lack of Flash has it's drawbacks but a lot of the news sites I frequent are moving away from Flash. I frequent a number of forums where Flash is irrelevant and those sites work without a hitch other than the occasional blank spot where an ad might go. The 802.11n WiFi makes for better throughput than my iPhone can muster, though the 3G about as fast as can be expected.
The GPS feature works very well, in fact it it works better than on the iPhone. I suspect that the larger form factor allows for a higher gain antenna.
The on screen keyboard works very well (I'm typing this on it), though no virtual keyboard can take the place of a real mechanical keyboard.
The battery life is very impressive. The 10 hour figure seems to be pretty accurate.
The iPad is heavier than I'd like at 1.6lb, but I guess that's unavoidable due to the large battery and large glass screen. I don't think I'd want to trade weight for a less scratch resistant screen and shorter battery life.
From the hardware to the OS, it's an elegantly designed device, It's as much of a game changing device as the first iPhone was. It isn't perfect, but that's what updates are for. Remember that the first version of iPhone OS didn't support third party apps and now there are over 200,000.