Verdict: Recommended. But be ready to filter out some strange anecdotes and slightly whacky techniques.

I first read this book in January and decided to wait to review it till I could figure out if the methods in the book were practical. When I read the book, I was a rather skeptical. Some of the anecdotes make the author seem a few cards short of a full deck. E.g. throwing other people's stuff away without asking them, dumping unwanted stuff on a younger sibling, etc. So, considering that the average person is unlikely to act in such a (inappropriate?) way, I was wary; particularly of the technique where you're expected to touch each thing to determine if it brings you joy. I decided to let the ideas, bereft of the awkward bits, simmer for a few days before deciding to put them into practice.

About a week later, I realized that the ideas could apply, not just for physical possessions, but also for a lot of ideas and thoughts swirling in my head. I'm one of those people who has at least 1 side-project going on in addition to a serious hobby. I was often left feeling like I'd never done enough and there were lots of incomplete projects (mostly software) or things I wanted to get better at (photography, playing the saxophone, etc). Truth be told, I take on way more things than I realistically have time for. These would weigh heavily on my mind whenever I spent time broadly reflecting on how things were going and whether I'd made progress in my various endeavors.

Around the same time, in January, I'd started trying to re-organize my life (yeah, a bit radical) using the techniques outlined in Getting Results the Agile Way and there are some common threads in both books which apply broadly to better self-organization.

Eight weeks later, I re-read the book, this time prepared to filter out the awkward bits and focus on the core. Looking back at the last few weeks to see what I actually used, here's what I've learned:

1. Tidying up is about getting rid of things, not finding places to put (hide?) things away.
2. I interpreted the part about "keeping only the things that bring joy" along slightly more practical lines of "is this something I will use going forward?" This interpretation seemed a little less "fluffy" to me.
3. Tidying by category is an excellent idea. Bringing all things of the same category together gives a clearer big picture and makes it easier to decide what to get rid of; hint: bigger pile means you're likely to dispose off more.
4. From the part about dealing with mementos: I found that when applied to my mind, it helped me to eliminate wasteful brain cycles on past, incomplete side-projects and hobbies that I'm unlikely to resume. The focus has shifted firmly to my on-going and near-future side-projects .
5. From the technique to designate a place for each thing: I'm a "work hard, play hard" kind of person. The "play hard" part becomes difficult when I don't feel like I've accomplished the "work hard" part; not because I didn't work hard, but because of distractions from work remnants. Separating the two clearly has reduced the interruptions in my head, resulting in better focus and higher productivity.
6. I used to store stuff by fine-grained categories which made things more difficult to find. Broad classification for storing items works well. Fewer places to look for things, consequently things are easier to find.
7. "Empty your bag everyday" didn't work for me. I have disparate items that I carry in my bag. They get stored in different places and I found that I spent more time putting away and gathering things that needed to go into my bag, sometimes forgetting items.
8. Bulk buying is economical and unless I become severely space constrained, I plan to ignore its description as hoarding.

Tidying-up definitely has a positive effect on other parts of my life. There are fewer distractions, less visual noise, and reduced guilt from having to see unused items (in my case mostly books).