It all depends: what are your goals?
[Note: my background is as a programmer, but I've been making a living as a tech writer/speaker for the last 12 years. After 15 titles, dozens of magazine articles, and speaking internationally, I think I'm at least as qualified as anyone else here.]
If your goal is to make money, don't bother. Really. I know a lot of people in this business, and very few make a decent hourly wage from writing. Of the ones who do make a living at it, all of them write for beginners (tip: there are always more beginners than intermediate or advanced users).
IF you're currently working as a consultant and
if you want more consulting gigs with bigger companies at a higher price and
if you've been offered a book contract and/or speaking gigs
… then go for it.
Don't think of it in terms of work with low compensation; instead, think of it as just part of the training and prep you already do in order to get those consulting jobs.
Screw writing articles for magazines/sites that don't pay — or say you'll write for them, on the condition that they run your article without ads. If they're making money, you should be too. However, if the magazine helps you get those high-profile consulting gigs, see the advice in the previous paragraph.
Speaking gigs, though, are almost always worth it. At a minimum, you'll meet other presenters, which is how I've met some truly amazing people. Networking opportunities abound.
On the other hand…
IF you have an amazing idea for a great book that no one else has written and
if you can't rest until you see that book in print
… then go for it.
In this case, it's about love, not money. If you can handle a life where this book doesn't exist, then don't write it.
But it's really all about where you want your career to go. If a book helps you get to that place, then see if works for you.