I have a Giro shaped head, so that's what I buy. Some of the Giros do come with the little dial thingy in the back (similar to what Bell uses), rather than the tabs. I only buy dial-adjust helmets- I love being able to adjust it one-handed.

The current helmets are a Giro Kaya and a Giro Skyla. A $30 helmet protects as well as a $230 helmet, as long as it fits properly, and I don't feel guilty or upset if something happens to one of my cheap helmets.