The deficiencies look quite obvious to me:
http://arstechnica.com/gadgets/news/2010/05/android-tablet-p...I'll put it this way: The iPad would not be a compelling device if it merely ran iPhone software at a higher resolution.
Hardware-wise, the iPad is nothing but an iPod Touch with a giant screen and a giant battery. Software-wise, it's everything but an iPod or iPhone; the use cases are very different. A touch-surface that's 5 times larger than an iPhone enables a much richer and more sophisticated UI, and this is evident in the iPad SDK, Apple's iPad software, and the successful 3rd-party iPad software.
Google needs to define their tablet HIG, they need to update their SDK to implement their HIG, they need to update their built-in apps to take advantage of the new SDK, and they need to get their 3rd party developers on board. All of this takes time, and I would not expect it to take shape before the spring or summer of 2011 (they're still "feverishly working" to get Android 2.2 out the door). Anything less will result in a product that's not as compelling as the iPad.
That said, I have no doubt that manufacturers will try to sell Android tablets before the Android OS is ready, and I have every confidence that those tablets will fail in the marketplace. But eventually there will be compelling Android tablets.