Great to a certain point
If you are an association with parent/company members, this is probably not the AMS for you. It is very dificult to manage. For indidividual memberships, it works very well.
YM just did a major upgrade with their email system to improve deliverabilty, but there are still some major improvements needed – such as making the templates more user friendly and having them look more professional. The WYSIWYG editors (for both email and the website itself) could also use some updating as they seem to have fallen behind the times. Some users have explained to us their process for renewing membership and registering for a meeting can be confusing – which I can agree it can be – but some of it is a learning curve to a new system.
It is difficult to find an AMS that meets all of your needs well. YM might be the one that works best for you depending on what exactly you are looking for, but don't expect it to be an all-in-one without any trade-offs.