Crossloop Pro user
It's not bad, but the install/connect procedure can be a little arcane for new users (having to skip creating an account, etc). And if they initiate it from the 'Share Screen' button on your Crossloop.com page, sometimes the auto setup/connect procedure just doesn't work and you have to get the pin number anyway. Nor does the reboot and reconnect always work properly. Also, doesn't work unless a user is logged in, so tools that can properly run as a service aren't fully replaced by Crossloop.
Once installed it's pretty simple and I do like the feature that (if it works) users can allow you access for a set amount of time and adjust/revoke it whenever they please; I haven't come across any other tools that would do this. You could setup some sort of workflow where the user registers a ticket with your helpdesk, hits the 'Share Screen' button, sets it for 24hrs and walks away. That way you can get to looking at it when it's convenient for you. If all the functionality worked all the time without error or issue, it would be amazingly useful.
All in all, it's pretty decent (especially for the price!), especially the ability for the user to control the availability of connection through adjusting the timeframe and the changing of the pin [just about] every time the program is run -- puts the concerned user's fears to rest about security etc. However, I'm still looking for something that's a little easier for the average user to initiate connection (less steps) and that could be used in a business environment.