I use mine all the time, be it browsing whilst watching tv, which could be done with a tablet yes, but that's another £500 to spend, or when I'm travelling, or when working. I have a desktop for day to day work, I wouldn't be able to put up with a laptop, especially a 13" one as my main machine but when out its very useful. There are times when I don't need a full blown laptop though, that's where a tablet would come in. A day out or as a backup and basic processing device for my camera, for that android just doesn't cut it, unless of course you can run CS5 with high resolution RAW files on it, or tether a camera to it!
Sometimes a basic tablet would be nice but this is where it goes back to a comment I made in the CES phone thread, syncronisation would have to be a lot better than it is now. Its a pain having to sync two devices together, even with live mesh, 4, with different OSs in the mix would be a nightmare. When we can automatically sync documents, pictures and films between different devices, which will hopefully be soon, then if I had the money id contemplate one.
As a media device to sit in the living room where you chose your film you want to watch or browse tv channels they are going to be excellent (and so far Panasonic, Samsung and Sony are using them for just that).