Only the item the iPad was bought to replace - my Sony VAIO TZ150N. In many ways, it superior to the iPad - it's a full PC with 320GB hard drive and 2GB RAM with built-in DVD-RW drive, yet it weighs 2lb, VGA and HDMI ports, USB ports, modem, ethernet, wifi, GPS, all for a mere 8 ounces more than the iPad. Even has built-in cellular broadband capability like the iPad. Mac fans note: the TZ150 designer was recruited from Sony to design the Macbook Air. It is, quite simply, a fantastic piece of tech.
However, as I have a more powerful full-size laptop for home, it's overkill on the road; despite all the capabilities it has, I pretty much do the same tasks I'm doing on the iPad. And with the iPad, my broadband data connection is cheaper and doesn't require a contract, and battery life is about double what I get on the SONY, even with the double-cap battery.
Take the $320/year I'm saving with AT&T plan v. Sprint PCS' unlimited plan, throw in the $500 my TZ150 should bring on Craigslist, and the iPad is free!