As long as the competition simply tries to copy the iPad, they wil have a hard time beating it. Yet, Apple with its closed business model, will not easily get a dominant market share for a long period, but will be a major force of influence.
I do own a tablet which, except for Germany, is not quite popular; at least not here in the Netherlands, yet it has raised a lot of interest from my colleagues here, by the way I use it. I dropped the MeeGo from it as it is not mature at all yet and put Ubuntu netbook mix (10.10) on it. True, it's far from where the iPad is looking at pure tablet things, but extending it with a usb-.DVI connector and connecting to my 1920x1200 screen it suddenly turns into a perfect dual screen notebook replacement and yet it still is the only thing ( 1kg) that I need to carry around (I happen to have a display that size both at work and at home). Bluetooth keyboard on both desks and a very tiny usb based one for the road to finish things. Plug in a DVB-T stick and watch live TV on it. Mine doesn't have 3G but I can use my N900 phone for tethering. A 3G model does exist as well though. Oh yes, forgot to say it runs a dualcore Atom, so everything running on a Linux PC simply works (or even Windows, if you want/have to).
Ok, I'm not saying my use is "the way" to use a tablet, but I think it shows the potential if you start to think outside the Apple build iPad box. I bought a second one a few weeks ago for experimenting and I can't wait to see what more I can do with it.