What does GoToMeeting do well? Quickly and easily setup a meeting that has great presentation sharing features and UI chat. Sharing a link within a meeting invite or email is all it takes for a meeting attendee to join and includes dial in details. Can easily see who has joined and who is muted, etc. Providing meeting attendees a visual of your presentation deck with the organizer able to flip through the slides without telling the attendees which slide to view, etc. is priceless. It is much more engaging which helps users retain the knowledge and discussion topics much better.
What does GoToMeeting not do well? Sometimes connecting to a GoToMeeting prompts for software to be installed which often causes technical issues right before a meeting, which is undesirable. This is especially true for users with strict controlled PC/Laptop settings that don't allow software to be installed without admin privileges at your company.
What do you wish you had known about GoToMeeting before using? Make sure that users joining your meeting are able to with their current business firewall/software restrictions. It is always a nuisance if users are not able to join or join late because of it. Should test beforehand.
Have you used a competitor to GoToMeeting? If so, how does it compare? Microsoft Teams, Skype for Business, and Webex all have similar offerings, each with their own pros and cons. GoToMeeting is a good option for non-enterprise solutions where you need to quickly setup a meeting without all the hassles of creating accounts, etc.