I have just not long bought my Xen licence and will be doing the migration shortly. I am currently running Vbuletin 4.2.2 CMS. Would have liked to stay with Vbulletin as I am already am knee deep and know the software very well but I really needed a responsive design website. Vbulletin 5 was a no go as I did not likehow it looked or what you could do with it as well as the horror stories I have heard. I will partner Xen with Wordpress, so all new to me.