It would be a very useful artillery tractor which I believe it was indeed attempted to be sold as (unsuccessfully). A part of that lack of success was that it had extremely poor (actually, my understanding is pretty much non-existant) rough terrain capability. It needed at least halfway decent roads to work. Plus, it was highly complex. There were a number of things that just made the technology too immature to really work out until the late 19th century.
Now I know what some of you are thinking, if they had just focused on maturing the technology, maybe they'd have it sooner. The thing is, though, is that they did. Steam cars had been continuously re-invented from the late 18th century though when they were finally perfected in the latter half of the 19th century and began to see wide agricultural use, and started to be adopted as artillery tractors. People did think it was a good idea at the time, it just took a while to figure out enough details to make it suitably practical. And until they could figure out how to make a vehicle that could go off-road (and by the time they did it became the domain of the internal combustion engine) it would've been just as good to use rail lines for long-distance logistics anyway.
