I collected 1.5 cord of locust this year, hoping it'd be something special but my experience was mixed. The main problem was the amount of ash it produced - more than any other wood I have burned. It was as dense as the densest eucalypt we have locally - we are in a higher rainfall area so have faster growing and less dense eucalypts than some areas - so the BTUs were there, no doubt. And it was great to split, best splitting wood I have come across, I reckon. I've read about the longevity in the ground but also one other thing about it is the torsional rigidity. I had one bit that split off by itself when I was splitting the bigger rounds. It was about 4 inches across and 15 inches long but a fraction of an inch thick, just a sliver. It was almost impervious to torsion, I was impressed! No doubt, for building things, it'd be great in many ways.
I burned it at night primarily and it did the job getting through but burning it exclusively through the day didn't work well. You end up putting more in before all the coals have burned down and the ash smothers them so they don't burn out fully. End result is a full firebox that won't burn down properly. Mixing it with lighter stuff would help but my other wood is of similar density so that wasn't an option. I needed pine! For me, I have eucalypts that are as dense without the ash so I won't go back for more locust but I'm sure that it will serve you very well in the right circumstances.