I see two very different comments, and appreciate both.
We have used "Sena" SMH 10 , for 5 seasons. They are adapted from the motorcycle crowd, they work well for communicating, we are a 140 Y.O. team and both wear hearing aids.
Pros: The close proximity of the mic helps clarity and noise, more economical than Terrano, they will do bluetooth music although we have never used that feature. Work fair in connecting to cell phone.
Cons: They are a pain to mount, as they are not made for a bike helmet, it's a total "engineer it yourself" mount which I realize is not for everyone.Wind noise seems to get the upper hand in the 18-20 mph range.
Due to the fact they are mounted on one side of the helmet, the weight "tips" the helmet.

This Sena is NOT voice controlled, so no delay, battery life is over a days ride use.
The Sena batteries are not replaceable, so I had planned on "upgrading " to the Terrano, Alan's comments make me wonder if that is an upgrade.
I do notice they have more products available on their website (sena.com)
Just some thoughts
R&J