I like that it is easy for me as an administrator of our website to keep track of all my member's information in one place and easily see who has logged into or out from our site as well as their contact info if needed.
I wish there was more flexibility with how we could customize this application but I guess they are working hard to improve it! It would be nice if you were able to make your own fields instead of having them pre-populate. This makes it so much easier when creating new accounts etc. We have been using Member Link since 2006 and love being able to store all the membership data in one spot.