Projects like OpenDNS (not DSN BTW) don't really fall into the good or bad category. There are good and bad aspects about it, and it's a judgment call everyone has to make for themselves.
Personally, I think they're overselling their anti-phishing feature quite a bit. I also don't really think that the DNS layer is the proper place/way to address that problem. However, if it stops a few people from being conned out of their retirement funds or something like that, then it has done some good. Their much vaunted cache of domain names could also work against their anti-phishing efforts. If they cache the domain of a phishing site, it could remain in that cache for a very long time if no one spots it.
Also, while I'm glad to see they're very upfront about how they sell advertisements on placeholder pages for mistyped URLs, I'm not a big fan of that practice in general. It's too easy for some advertiser that hasn't found a line yet they won't cross to get in there. They may make a legitimate effort to try and screen out those sorts of companies, but sooner or later a few will get through.
I'm also curious to see if they'll be able to keep up with demand if it spikes. While DNS queries are hardly bandwidth intensive, they do add up if you're talking a few hundred or thousand requests per second. A caching system will help, but it has its limits like anything else. I don't know that advertising revenue will ever be able to cover the costs of bandwidth and hardware needed to maintain everything.
So if people want to use this service, I think they could do far worse. However, I'm not quite sure I'm ready to jump on the bandwagon just yet.
I just ran across a operation that seems to have some very good features with little if any drawbacks. There is a site http://opendns.com/faq/ that intercepts phishing attempts and opens DSN services. I haven't used it long (1 hour) but I have not detected any side effects. I like the fact that no new software is needed. It is activated by adding two DSN numbers. I would hear from others on its use. I run XP-PRO on DSL. Bob G