I ran across opendns.org the other day and decided to try it.
There was a definite speed boost! I have Verizon FIOS and the OpenDNS servers are more responsive than Verizon's DNS servers. I've noticed that most pages now load in about 3/4 of a second (time to look up the DNS name, fetch the page, and render it). I use fasterfox to time it.
OpenDNS also provides some interesting reports. You can turn off the DNS logs if you like (privacy and all), but I found them useful. I have a cron job that runs every 5 minutes and fetches my mail via POP and mails it to another account. The cron job had done over 24,000 DNS lookups of the same IP address in the last 8 days. My router is supposed to be caching those requests (isn't that why you run local DNS?), but its easy to see that caching is not happening.
Also, OpenDNS gives you the ability to block domains, and automatically will block phishing and pornographic sites if you want. This can be pretty useful, for kid-safe and normal-user-safe browsing.
I've been pretty happy with using the service so far - especially since it is free. The only thing I've noticed is that I haven't seen any *nix update clients. Anyone found one that they like?
Update: here are some screenshots from their interface
Sample blocked domain