I rode a Pro-Tec shovelhead 2 for a few months after I fucked my face up last year, and I had a few observations.
(1) I'm not at all claustrophobic (I was stationed on a submarine a few years ago), but it took a long time to get used to that helmet. I felt like I couldn't breath, and my breathing rate was through the roof. It could have been the lack of airflow to my face or something, but I was getting this shortness of breath feeling and it made me freak out a bit.
(2) On that particular helmet, the chin bar was right where I wanted to look to spot my landings. I eventually got used to it for the most part, but every once in awhile, I would be in the air trying to find my spot, and all I saw was chin bar.
This was all riding bowls and modular park.