It IS a blast, at least for a while - after doing it all day every day for a few years the novelty wore off for me. It was still a pretty good job for a young single guy though, at the time. I never drove one of those two stick trucks though. That's really old technology, about on a par with front engine indy cars, and not used that much after the seventies I would guess. Having a lot of gears like that was a response to the underpowered engines of that era, they had a pretty narrow usable rpm range. I think some guys did keep using them because they could get a double overdrive and, I guess, higher top end (the two sticks are basically two linked transmissions as I understand it).

My 87 Peterbilt had a 13 speed, which is really a nine speed with a splitter for the top four gears. The way it works is, one low "granny" gear, four low range gears, and four high range gears that can be split in half, all done with one stick. The splitter wasn't really necessary but nice to get the best rpm for some speeds, most fleet trucks didn't have that, just 9 or 10 speeds (as I recall 10 speed was like a nine but you used the "granny" gear in the high range too). There's video of these on the youtube too if you are interested, though I looked at a couple and it was kind of hard to see what they were doing.