I have owned a tractor + backhoe attachment for more than 10 years. While most of the hours on the tractor did not involve the backhoe, when we did use it, it has been an excellent tool. Looking back, I definitely got my money's worth out of it, and for my situation, it was the most practical and cost-effective way to get my work done. That's not to say other equipment choices won't be better in other situations, but for me, it really did the job well.
So, when does an add-on backhoe make sense vs. say, a mini-ex or a true TLB? I'd say over 1,400 hours of tractor operation we have maybe 300 hours of BH time, spread over all 14 years. If I had to rent something for that many hours, it would have cost as much as the BH, and the convenience of having my own equipment handy whenever needed was worth it to me. Sure, I could have bought a mini-ex, but then I'd have to also invest in a bigger truck and trailer to haul it to the places a mile or two down the road that my tractor could easily drive to on its own. One of the small construction grade TLB's would have been workable, but a) it cost more and b) it was optimized for digging work, which was less than 1/4 of the hours of use. So, contrary to what some folks say here on TBN, there is a useful place for an add-on backhoe. Not all the time, but for many folks, it does make sense.
Was the "changing seats between tractor and backhoe" thing a problem? Well, yes, but not as much as you might think. Maybe it's just me, but I was on and off the BH anyways with my projects, checking my work etc. And, the times I've used a mini or a true TLB, I was still on and off the machine quite a bit, too.
I don't know anything about what you expect to do with a backhoe, but if you do decide it makes sense for your needs, here are some suggestions.
1. Size and weight matters. The smaller the backhoe, the more you have to re-position. Your tractor would handle a 7 ft. hoe, I think, and that would need to be moved around a lot for extracting decent sized stumps, for example.
2. A subframe mounted backhoe is more capable and a better mounting arrangement for the tractor.
3. The backhoes offered by the tractor manufacturer are specifically designed for the particular model of tractor and can have some advantages in the way they fit to the tractor vs. the non-OEM backhoes that are a more generic design. Not a knock on the non-OEM backhoes... there are some excellent ones available. May or may not save money, but remember, you usually get what you pay for.
Excuse long-windedness. I hope something here might be useful.