I haven't seen this posted before - my apologies if it was and I missed it.
I would really like to see a private message system on the new CH site. The Invision message board software has such a system built in and I've found it really useful for communications that don't really belong on the boards due to site policy.
Historically CH has discouraged "chatty" posts since they dilute the food oriented content. Fair enough. They also have taken a firm stand against using the boards to organize events for the same reason. Again, fair enough. There are other boards that have different policies but I understand CH's reasons and respect them.
But human nature being what it is, people still want to arrange dinners and sometimes they have a comment on a specific post that doesn't fit within the guidelines. A PM system makes this easy and removes a lot of the temptation to post things on the boards that shouldn't be there.
Sure, you can post an email address on your profile page but that requires a certain potential loss of privacy. (Yes, I know that you can create a special email address for CH messages but that's a real pain. I've already got 4 email addresses and I really don't want another mailbox to check.)
A PM system wouldn't require you to publically post your email address but would allow you to privately communicate with any CH user. One other thing for those not familiar with PM systems - they also support blocking. If someone who hates your favorite restaurant starts sending you annoying PMs you have the ability to block all their future PMs.
I've had experience with these systems for 5 years and they work really well.