I went from an '88 R100GS to a 2000 LC4E, and expected to be a bit disappointed with the KTM's road manners. As it turns out, I love the KTM, and have no problem doing 300 mile+ days on it. There are a ton of aftermarket parts available, the bike is quite capable as a light dual sport tourer...as has been said, with the exception of the TE610, there is really no other dual sport as dirt worthy and as capable on the street.
I personally prefer the E to the Adventure, simply for the reduced weight and for the fact that the enduro has much less plastic to damage. I find that, even with the stock headlight mask, the E is perfectly comfortable on the road, as long as you keep the speed below 70mph.
Off road, you can drop the enduro all day long (I know from experience) without doing much damage to it.
The bike is fun, capable, fast, outstanding off road, and a blast on back roads and in the twisties...I say go for it!
'05.5 KTM 950 Adventure
2008 KTM 450 EXC-R
All Orange, Baby!