Greasemonkey rules. Not only for users, but for publishers, too.
The reason it's good for users is obvious: It gives them total control over customizing content within their browsers. If you don't like the layout of a Web page, you can change it. If you want to add features to a particular site, you can. If something on a Web site bothers you, you can remove it.
The reason it's good for publishers is more subtle: It's free usability testing and free product development.
(And let's ignore ad removal for a moment. That technology has already been available, for years, in many other ways -- notably browser plugins such as Adblock. There's nothing novel about ad removal via Greasemonkey, from a publisher's standpoint.)
Look at the Greasemonkey script repository. Aside from the ad-removing scripts, each site-specific script falls into one of two categories:
- Fixes a usability problem
- Adds a feature
These types of readers should be embraced, not shunned. It's the technological equivalent of Dan Gillmor's well-known line, "My readers know more than I do."