GEDMatch

For years, I avoided GEDMatch, fearing as-yet-unknown risks of publicly posting DNA. Recently, having discovered that close relatives had already posted their DNA on other DNA matching sites, I decided to try GEDMatch. Here are my first impressions.

Cons:
(1) I found no first cousin or closer relatives on GEDMatch, making my DNA a sole source for identifying close relatives. I may have my DNA deleted from this service.

(2) Because there are no close relatives among my matches, it is exceedingly difficult to identify any matches.

(3) Gathering match segment data, needed to determine common segments between matches, is tedious using the free version of the service. This information must be gathered individually for each match. There is a paid version of the service, and I don't know if gathering segment is any easier with it.

(4) For now, as a newbie to GEDMatch, I'm concerned about determination of amount of shared DNA. Often, a cM amount that is given in the list of matches does not correspond to the sum of the segments. Often, when I find that the same individual is listed on a different DNA analysis service, the amounts of DNA shown by the two services is significantly different.

(5) The ethnicity estimating tools are much less precise, geographically, than available at other services.

(6) There is no ability, at least in the free version, to annotate or tag matches as you identify them, something available in the other services.

Pros

(1) It's free.

(2) Using the free version of the service, it is easy to gather a list of matches, a list of common matches, and a family tree (if available). Note that I use Pedigree Thief (a Chrome extension) and Genome Mate Pro to harvest information and keep track of my research. 

(3) Email addresses are available for each match. (Though I have not tried any, so don't know to what extent they are valid.)

(4) There are many matches at GEDMatch that I don't find on the other services that I use. However, since I'm having trouble identifying these matches, this may not be useful.

(5) You can upload your DNA file from any testing service. Ancestry and 23andMe do not allow this. MyHeritage does allow this, though I'm not sure what limitations they currently impose on free uploaded DNA data vs. DNA analyzed at MyHeritage. 

At this point, I would not recommend GEDMatch unless you are an advanced DNA user with an extensive tree and many DNA matches identified with other services. (It's possible that the lack of close matches is an anomaly for my DNA and others would benefit more. I have no knowledge of this, yet.)