It’s different from an iPhone, mostly because it’s bigger. (BTW, note that a new version of the iPad is expected shortly, so I recommend holding off for a bit.) I don’t have much experience with the onscreen keyboard, but if you want a physical keyboard, you can get Bluetooth keyboards as accessories. Some are sold as part of an iPad case.
I have a couple iPods, 2 iPhones in the house (mine and Mr. Athena’s) and we bought an iPad a couple months ago. It’s a whole lot different than either iphone/iPod - the larger screen alone makes it a whole different thing.
It’s WAY easier for web browsing, the apps are easier to use, it’s just generally better than the iPhone. We fight over who gets to use it. Highly recommended.