My plan was to get an Android tablet. I have been very happy with a Droid and now a Droid 2. My plan was to get a tablet, since I was familiar and happy overall. Advantages--don't have to rely on Itunes to transfer files (just simple folders), good voice commands, GPS with voice, widgets, live wallpapers, a working Google Voice app, Flash video, etc.
A work laptop broke down earlier than I expected. I decided not to hold out and instead go for the Ipad. I believe that Android tablets will definitely be opponents of the Ipad. There will be more options, they will be cheaper, and they will have some advantages (some of which I mentioned above). I think the Android tablets will be behind the curve a bit and will have already lost much of the market to Apple.
I think a lot of people with the Android phones (who are happy with them) will migrate toward the android tablets once they are out.