I think I'll try one on this evening. The other option is the Nolan N43 Air
http://www.nolanhelmets.com/n43trilogyncom.htm
same sort of idea - an open faced helmet with a chin bar which can be attached. I have two helmets at the moment, a Nolan open face and an AGV closed face. I like the open face because it feels more like I'm riding a bike than the closed face which has the car windscreen effect of isolating you from the environment somewhat. The only problem is at speed the visor slams shut of its own accord, the wind getting past the visor makes it difficult to see and in the eventuality that I feel like face-planting the tarmac, I'm going to need the name of a very good maxillofacial surgeon.
These helmets seem to offer a much larger field of view even in full face mode, the ability to be completely open face, and at least maybe a little protection in the chin bar (though I know it's not likely to be much)