Personally, I prefer not supporting unethical registrars, and especially registrars like Godaddy that are in bed with domainers and spammers. If I need to worry about a registrar ripping me off by pseudo-frontrunning (since frontrunning is technically illegal now), then I wouldn't take my business to that registrar in the first place.
Hence, I just search for domains on the registrar I've selected to purchase the domain through. In almost all cases, this is DreamHost's registrar, which I can use right out of my web hosting panel. This also means when I purchase the domain the hosting gets set up simultaneously. It's just less of a hassle all around.
I think if you're using a legit web host whose primary revenue source isn't domain name registration, then you can be fairly safe that the registrar they run or use is also fairly legit. I.e. if you're using Rackspace, MediaTemple, Gandi.net, etc. then you should just search for/register domains through them. You can also be pretty confident in registering domains through Google Apps.
Web hosts I'd be a little more wary about: HostGator, Bluehost, and obviously Godaddy.