We are planning to use Maxbotix XL-EZ4 this year on our robot and so far have had great success with them. They are extremely easy to wire up (strait into an analog input) and we get cm accurate readings from them. No need for a ping channel unless you are planning on Daisy Chaining them and that's just so they don't interfere with each other. There is only one ping channel no matter how many sensors you want to wire together, much easier than the SRF08s.
http://www.maxbotix.com/MB1240__XL-MaxSonar-EZ4.html