I decided to give the new 507 with Vulcan reticle a try because I've had limited practice time in the last year. While I usually have no issue finding the dot on an RMR or Acro, I have had some problems when shooting SHO or WHO, or when I get a bad grip when drawing. I've only had the new 507 for a few days, but my initial impressions are very positive. The outer ring serves it's purpose perfectly. It is also very intuitive and makes alignment easier with very little practice.
I wasn't sure how much I would like the chevron as a dot replacement, but it's growing on me. The outer ring with the donut from the 407co would be an interesting reticle option as well.