I have a zoom, 4g/wifi. I get a lot of use out of it. Its handy, but if I wanted to be productive, I'd take a laptop. Some of the tablets seem to want to bridge this gap - but I'm content with my tablet being a TV/receiver/htpc remote, game, Netflix/movie/music/book, GPS, email/Facebook/phone/SMS text machine - and for productivity stuff such as excel/remote desktop/SSH/SQL client/etc in a pinch.
Most tablets have Bluetooth so any really can have a mouse and or keyboard - but if I have to take a laptop bag, I'll take the laptop. Otherwise any semblance of convenience is lost, not to mention trying to fit a square into a round hole. As a convenience device it rocks as most tablets do.
I work from home, primarily on a laptop and go away to the site in a different state monthly. The tablet helps minimize how heavy that bag is, while still allowing me to keep in touch with the family and to allow for some entertainment while on the road.