Since purchasing the iPad, I've constantly been amazed by how fast everything works—switching between large apps is no longer a game of roulette, and browsing the web is a breeze.
I ran some tests on Safari on my iPad, just to see how things compare to my MacBook Pro...
Here's the screenshot from my iPad (14068.6ms):
And from my Mac (406.8ms):
Here's the screenshot from my iPad (took about 5 seconds):
And from my Mac (took about .5 seconds):
It looks like, in terms of raw power, the iPad isn't anything amazing, but it isn't nearly as slow as my iPhone (iPhone took SDFJSOIFJD ms). On most sites, I don't notice any lag while browsing on the iPad. Every once in a while a JS-heavy page takes about 2-3 extra seconds to load up all its widgets, but this is definitely tolerable. The decision to ditch my personal laptop is getting easier and easier...
The Bottom Line
Just basing things off the SunSpider test on Safari across my Mac, iPhone and iPad, you can see a very large gap between a 'desktop' Mac vs. the iPhone OS devices. This is understandable, as the iPad and iPhone are built for a completely different purpose than a laptop—they are not 'desktop replacement' computers, but rather mobile computing devices.
iPhone (Cortex 600 Mhz A8): 17002.6 ms (baseline)
iPad (Apple 1 Ghz A4): 14068.6 ms
MacBook Pro (2.53 Ghz Intel Core 2 Duo): 406.8 ms
Also be sure to check out my comprehensive review of Apple's iPad.