Practicality of driving it on public highways is just about nill. I owned one for a year or so, but really dreaded driving it around town. Not that the attention it draws is bad. Its the vehicles driveabilty thats a problem. They arent meant to be driven 55+ mph. Badly insulated cabins, extremely noisy drivetrain/tires. Steering like a tank, etc.
As for its off-road capability, none can compare. Seriously, its that good. I drive a Hummer now, and I cant imagine doing some of the stuff I did in my Unimog with it. Its just the best value around for a cheap, capable 4X4 plaything.
Parts are so easy to attain now compared to when I had mine about 8 years ago. You see Mogs advertised everywhere. And the prices have come down since the Swiss Mogs got surplussed a few years ago.
Working on them isnt too bad if you have half a brain. Main problems are with the enormous sizes of some of the parts on it. Definitely require a chain hoist in the shop. Mine had the PTO winch mounted to the bumper. It was so heavu it sacked out the front springs and wore tires out. But to remove it from the truck required the chain hoist.