Gedmatch has added a forum. Very simple format, organized by surnames and topics. Once you find something you find interesting then you can add your name and information or comments. One problem is that there is not way to get a notification when there is a response to something you have posted, so it is difficult for people to know that you are responding unless they manually check it often.
The best use is if you have a surname and are just looking for random matches to see who you might match in an area or with a particular surname.
With three individual tools this has been one of my more useful new tools.
1 Gedcom to all...here you add in your Gedcom ID and it gives you matches to other Gedcoms by name that are the same and similar. According to the size of your personal Gedcom, the length of time to run this can be long. An hour or more. Then the storage of the material and that a lot of the information is not even a good match makes is something to save for a rainy, boring day.
2 Gedcoms...This one is better. You have a target person that you are working with and you can use it to compare your Gedcoms. I had a gal from the Stewart's and we were a match. Our Stewart YDNA did not match but when we ran this tool, we found we shared Wells as Grandparents. A good tool for if you think you may have more than one set of shared Grandparents. Is is dependent upon the accuracy of the information that you and the other person has entered, so I would recommend that a person verifies the families but it is a good place to get a lead.
Search all Gedcoms....I find this useful to search for new people who might match you on a particular surname in a specific location. Since it is dependent on the format used by the person who entered the information, I have found that if you keep search by state or county and then just do a search using a “find” tool for a more exact location that it works best. When you have a first and last name you really increase your chances of finding someone who you match. I found a family member of a Grandfather's brother when I had entered my Joseph Stewart and Newberry. This gives us a DNA respresentative of all three sons and one daughter using this method, so it can definitely help if you do not have family members that you can have tested.
Results do not list the Gedmatch Id so you will have to use the email address (it works best) to find the Id if you want to make sure you match before you contact them.
User Information Utility
This is the best. It is the only place to find a person's email address, Gedmatch Id and Gedcom Id. Also, if you wonder if a person who you match on Family Finder or 23&me or from a forum has been tested and are on Gedmatch, you can search for them using their email. Great for verifying paper matches that you have had over the years.