Personally, I'm happy to stick with ASCII. An isometric graphical representation of the map would, in my mind, be too difficult to display without massive headaches. Currently, since multiple "things" can occupy the same tile, how would an isometric graphic scheme accomplish this? I actually
like the ASCII scheme, as it's very simple and once you get the hang of things I actually think it's MORE intricate than a standard graphic scheme as it really lets your mind take control. Watching a white lowercase g get smashed upon some upward triangles is, in my mind, way cooler than seeing an ugly isometric goat whack up against a slope. The mental pictures more than make up for the current "poor" graphics.
Plus, honestly, I don't want nine-year-olds ruining the awesome game and forums that are currently populated by intelligent and masochistic persons like myself. Maybe that's selfish, but what do I care?
As far as "speed" goes, I'm not having any problems with 40d6. I've managed to push my FPS up from about 30 on the standard 40d release to a solid 200... with a 3x3 embark area and 110 dwarves. I don't use reveal and I leave temperature/weather/et cetera on. The only speed-increasing option I use is partial print, which REALLY helps.
Plus, I'm running DF on a laptop with Vista. Hardly the optimal setup, and I still bet I could beat 1k FPS with a 1x1 embark area (using the appropriate memory hack) and a small population cap (maybe 25). That seems almost unnecessary, as it seems the game was built for maybe 100 FPS.