Playing with an iPad, one of the first things you notice is its speed. Everything just zips into place. Our side-by-side tests comparing it with the iPhone proved that we weren't just imagining its snappiness.
The most telling test was loading Plants vs Zombies. To keep things consistent, we ran the test with the iPhone version of Plants vs Zombies on both devices. The loading bar flew across on the iPad, finishing just as the 3GS's loading bar was getting started.
But direct comparisons on less intensive apps yielded more even results. For things like Pandora and Epicurious, the iPad had the edge, but for opening anything that comes preloaded - Notes, Calendar, Contacts, etc - the iPad and iPhone 3GS were neck and neck.
The iPhone also kept up, somewhat surprisingly, while loading pages in Safari. The image-heavy Wikimedia Commons Hubble page took just about as long to load on each device. Granted, seeing that page snap into existence and take up the entirety of iPad's 9-inch screen is more impressive than seeing it do the same on the 3.5-inch iPhone, but strictly speaking load times were roughly the same.
Maps, however, shined on the iPad. It rescales beautifully with pinch to zoom and hardly ever falls behind no matter how fast you flick. The bigger screen also allows for wider pinches and thus deeper zooms, which the iPad handles without a hitch.
While apps are a toss-up - the bigger and more complex they are, the more they show off the iPad's speed - the iPad also shines in the most basic OS navigation. On the iPhone, hitting the home button is quick, but on the iPad it's instant. The difference might be imperceptible unless you hit the home button on each device, side by side, but it definitely contributes to the overall feeling that the iPad's just plain fast.
What remains to be seen is whether or not the iPad will slow down over time, as iPhones do. It seems like it would, but only after months of use and dozens of apps will we see if the iPad loses its zip in its old age. But for now, as pretty much everyone who used one in January and reviewed one this week has noted, this thing is fast.
Update: The good people at Furbo did some serious benchmarks comparing the iPad and the iPhone, and their results confirmed what we found in our informal tests: the iPad's a speed demon.
For native Cocoa Touch apps, Furbo found that the iPad was about twice as fast as the iPhone 3GS, which is about what we saw when comparing load times for Plants vs Zombies. On more intensive operations, the iPad ran almost 4x faster.
Head to Furbo for the full tests, including one that pits the iPad with the original iPhone which really shows how far Apple's mobile devices have come.