Apple announced today that the iPad Wi-Fi + 3G models would indeed be available in the US in "late April", technically the latest April date available -- April 30:
Wi-Fi + 3G models of [Apple's] magical iPad will be delivered to US customers who’ve pre-ordered on Friday, April 30, and will be available in Apple retail stores the same day starting at 5:00 p.m.
iPad Wi-Fi + 3G is identical to the Wi-Fi only models that shipped on April 3 (see TiPb's iPad review), but include an unlocked 3G radio for connectivity on the go, and aggressive AT&T plans for contract-free data at $14.99 for 256MB and $30 for unlimited.
That just leaves international iPads, which are still scheduled for pre-order starting May 10 and release starting "late May" in several additional countries, including Australia and Canada.
If you've go confirmation of your iPad Wi-Fi + 3G shipment, or plan on lining up at an Apple Store near you to grab one, let us know!