Well, I've had my (Branson) 42HP tractor with backhoe for a year. I'm very happy I got the BH (with matched subframe). It stays on my tractor except for specific days I need the rotary cutter instead.
It all comes down to how "developed" your property is, and therefore how often and for how long you need to dig.
I imagine if you've got your property essentially the way you want it, and most of your tractor work is *exploiting* it, a BH is unnecessary. Periodically you'll have special projects where it's useful, but if they're big and occasional enough, you'll do better to rent an excavator. And if you're property is *un*developed and you're clearing forest and cutting in roads, you also need a real excavator and/or other tools.
But for me, in between the two, it's a great jack of all trades that I use for 30 mins to 2 hours on most days I'm using the tractor.
1. Clear out silted up area around end of culvert on forest road
2. Create/deepen 15' worth of ditch
3. Flatten a 5x10' pad where I need it
4. Lift something up (have hook welded to BH) in tight quarters where it's tough to get loader end in
5. Push a small snag or pick up a small log
6. Slice up old pile of material so I can pick it up more easily (Piranha bar I got last fall helps on that)
7. Move a small boulder
Bottom line is it's like a pocket knife. It's not a real knife, but if you need to cut something small every so often it's great to have in your pocket.