I'm not a big clutter bug, but did her method and still found it really useful - feel so much lighter, and appreciate the things I do have more.
Mostly though I used it as a way to get my clutter bug DH to de-clutter. His stuff was driving me crazy because it made everything so crowded and hard to clean and manoever around. I think if he hadn't have got shot of a lot we would've ended up moving to a bigger house.
Basically instead of me nagging him, I used MK to nag him. So first I started doing it, then raving about it, then he got interested enough to read the book. Then I just had to keep the momentum up saying to him 'okay you've done clothes, what does MK say to do next? books, maybe you could start on that during DS nap this afternoon and I'll cook dinner'.
Now the house is a lot more sane and peaceful. It's probably helped our relationship a lot as I don't feel constant resentment as I squeeze myself past or try to somehow manage the consequences of his piles of stuff. He still has more than I would like - but I kept out of the actual decision making saying "as long as it brings you joy".
He's buying a lot less stuff now too - we had an Amazon Prime subscription and he had a constant stream of packages containing god knows what before. We also made a fair bit of money by selling some of the unwanted stuff - he had a lot of electronics stuff.
We're expecting a new baby soon, so this gave us the impetus. It took us around 3 months to do the house and we've recently finished. We even started on attic. But we decided to leave that now, as it's now tidy enough for us to feel comfortable (can see everything, and it feels quite spacious in there) and investing more time in it wouldn't improve our lives particularly.