The only problem I'm having is setting the userid into either session variable or a cookie on login with XF, looking through the code to find a good spot to do it. The script launched and added itself onto the page just fine though.
If anyone has some insite on where we can get and set the userid on login that'd help a lot.
I have cometchat also but have taken it down from my vb4 site. Vb4 loads slow enough as it is and with cometchat it made it a little worse. With the speed xf has I think cometchat would compliment it well and not slow down much at all.