I do 600 miles of urban riding on a 650gs (per month) and I really do think it's ideal. Our UK roads vary from passable to downright dangerous. I like that the GS is light, punches very well out of corners in the 5000rpm range, holds a line with great stability, and returns very good mpg. Since it's easy to max out the engine you can have great fun finding the limits of the bike.
As others have said, the Wee is probably a better long-distance machine in terms of bhp and comfort. If you do big days in the saddle of a GS you probably need an aftermarket seat and screen.
Fwiw I think I'd appreciate a DL650 from a fit-for-purpose angle, but I doubt I'd enjoy it in quite the same way as the GS.