Yeah I have winmo tablets at work for that sort of thing that we deploy out. Similarly I have a friend who's a graphic artist and has one of those wacom tablet display things. They're pretty cool.
But those are niche markets and tablets have been doing fine in that sector for the past decade.
Personally I just bought the new motorola android and it does everything I want. Solid email, messaging, web browsing, etc. I see absolutely no reason to purchase an iPad and only know 1 person that wants one - and I have a lot of mac-happy friends. The general consensus is that it's disappointing and they don't know what they'd use it for.
So while I see a continuing explosion of smart phones - I see very little use for tablets outside of established niches. The bottom line is this - you can't carry them around with you all day. So that means they replace home computers.. but they're not as capable and I think even your average consumer has some understanding of that. And even then.. why buy one over a laptop?
This is a fundamental problem with techy people. No matter how "neat" your service or product is - if it does not have a use it does not matter. A lot of us don't get that.