I used to have a ferret in college that lived with my boyfriend a few years after I graduated, then came back to be with the two of us after we got married and bought a house. She was so much fun, and such a character, but ferrets are SO much work! When I was in school, I let her run free in my dorm room until I came home after a long day out and found she could now make the jump from my bed to my bedside table. She had knocked over the plant on my table, a glass of water (making mud), and opened every drawer she could get to, pulling all of the contents out of every single one. It looked like I had been robbed.
After that I had to get a "ferret condominium" for her when I was gone, which was a huge three story thing that she actually liked a lot. I used to take her on walks, and like I said, she was so much fun. Like a kitten playing all of the time, kind of.
Mitzi came descented, but there was a definite odor that would creep up if she wasn't bathed very often. It wasn't really offensive or horrible, but like you said, kind of a musky, dank sort of smell. I'm really sensitive to smells, so I used to put her in the bath every other day, but it got hard once I was working and had less time. They will always go to the bathroom in the same place (always a corner), so you can almost potty train them. But again, the more often you clean it out, the less smell you will have, and cleaning her cage twice or three times a day takes time too.
The lifespan of a ferret isn't very long either, and that's a hard thing. Mitzi got sick and very weak around six years old, and we had to have her put to sleep, which was the hardest, saddest thing, but something we had to do. And from what the vets (we saw two) said, six years is a good life for a ferret.
Overall, I really enjoyed having her, and we had so much fun with her. But at the same time, I don't think I would ever get another ferret ... just so much work.