The flowers attract bees, and they like to suck on the pollen, so if you want bees than they are pretty useful. The taproots are good for the soil ecology. I'm sure somebody in your system likes the thistle there.
I also have thistle and next year I'm planning on harvesting, potentially freezing, and eating the cleaned stems. I tried some this year and it wasn't bad, similar to celery. Not impossible to clean, the fiddle factor is about a 3/5.
The other thing I want to do is find someone who is licensed to process the thistle into medicine and can do it in small batches. It goes for like 10 euros a bottle here. Granted, not a huge market.
100 thistle seeds goes for 2.36 on ebay. That's probably less than one plant.
It would be a good windbreak/barrier species if you wanted to rule out or go light on woody perennials. Mine gets 1.5 meters high and forms a nice bush.