I suggested OpenDNS some time back, and I still use it widely. If you haven't started using OpenDNS yet, you get Web Content Filtering (by category), Anti-Phishing and Malware site blocking, and you can use whitelists and blacklists for web access. There's a free version, which serves my needs (and my church's needs) rather well. You can read more about OpenDNS here.
I was surprised (and a little worried) when I read that Google was also offering a DNS service, named Google Public DNS. After reading the FAQ it seems that (initially) all Google is offering is faster DNS, nothing more. You can also read
OpenDNS's response to the Google offering.
Well, if you are using your ISP's DNS server and primarily use Google services, there's no good reason not to use Google's DNS servers; you'll get a bump in speed. However, OpenDNS gives you a bump in speed AND it offer anti-phishing and malware protection. There's no good reason to use Google's DNS instead of OpenDNS.
In short, if you're going to use a DNS service instead of your ISP's offering, I'd go with OpenDNS.
I don't expect that Google will stop at 'just offering faster DNS' but will probably start competing with OpenDNS more directly. Heck, they even have support numbers on the FAQ page that you can call?! If Google offers integration with DNS and Google Apps, and allow group or per user filtering options, that would strengthen their position against OpenDNS... but time will tell. The only advantages Google's DNS has right now is 1) name recognition and 2) easier to remember numbers.
Currently, though, OpenDNS wins hands down. Until Google offers more, OpenDNS is still going to be the huckleberry for other DNS services.
If you're not using an alternate DNS service, I'd totally recommend OpenDNS. Maybe you could use Google's DNS servers as your third and fourth in case OpenDNS is ever down, but I can't remember that happening.
EDIT: Looks like PCMag agrees with me, go with OpenDNS.
EDIT: I did plug in Google's DNS settings on a laptop -- it does work.