More will come to the market, Lenovo, HP and RIMM

It really depends on youself. Do you really need Android Apps ? Are some of Windows Apps important to you ? Do you need more mobility ?

Apple iPod/iPad doesn't support flash, and Android doesn't support Apple's quicktime, that I need for my online radio program. In my case, I prefer windows tablet. 

However, I prefer smaller size, 5-7" for the mobility. 10" is too big to carry around(in case I need big screen, I always can carry/use latop, which is much more powerful(there are 11-13 inch netbook/laptop on the market too, and they are just slightly heaver than some big 10 inch device). Keep in mind tablet usually you use one hand to hold it, another hand to operate it(using finger). If it's too heavy, it won't be comfortable. Another reason that I prefer smaller size because I can hold it  close to my eye in case I can not see things clearly(my eye is nearsighted, and start getting older).

If you love Apple products and need 10"display, I think $999 mac air with 64GB SSD, 4GB RAM and 11" display is better than iPad2.