I\'m looking for suggestions on Flash realtime servers. Currently, we use a combination of Moock\'s Unity and Red5, but there are a couple problems. First, we are moving to AS3,
I prefer red5 , it has been developed a lot these lasts months and i found it pretty stable. Once you get one app working the rest is easy and all the requirements you mention are available. If for "more stable" you mean the red5 source code changes too much , yes it does if you use the svn but you could choose one of the old versions and have a pretty good server for a while until you need to move to a newer version.
Also there is nothing like open source , you can change anything and share it so others can help improve it taking something and giving as well, the problem with a commercial solution is that even when you get proffesional support or a pretty stable product you will get the answer "we dont support customized servers" or such when you have very specific requirements, so forget about experimenting :P