I have just purchased a new iPad 2 and noticed the wifi dropout problem immediately. I have an iPad 1 and it is fine on wifi, but in the same location he iPad 2 is awful.
As it is ok on iPad 1, I was convinced it was nothing to do with the wifi network, especially when I noticed that it seemed more to do with signal strengths as even when searching for networks, that the networks discovered would also come and go even if I had not logged onto them.
After a lot of mucking about I have found out what the problem is. If you hold the iPad in landscape mode so that your hand is holding a the side with the home button, the wifi strength drops off until it disappears and the network drops out. If you hold the iPad on any other edge ( or simply lay it down so you are not holding it at all) you will find that the wifi is fine.
I am an electronic design engineer and it would appear that something in the physical construction of the iPads wifi internal aerial makes it susceptible to signal attenuation when holding it at the home button side. This is probably why apple cannot fix it with firmware, and it could be an inherent design fault.
Remember the iPhone that would work if you held it a certain way ? .....
Hope this helps some of you out .....