We use Join.me for our web conferences.
Join.me has an intuitive interface. It's easily customizable and simple to fire up a conference call when we need to.
It's possible to integrate with MS Outlook.. This plugin will automatically add your join.me details, including link and call-in number, to all meeting invites.
Join.me allows us to record calls and store the recordings for future reference and for any who are unable to attend the meeting.
We do see bandwidth issues when we have large conferences (150+ attendees). When this happens we have to ask people to use their phones to listen to the meeting to preserve bandwidth..