Not being able to change mini icons on threads at the moment.
The general use of vB having a better feel to surf around with. Or just how the old forum was. I'm much use to vBulletin from all my forum surfing years. But I'm pretty sure it's just because admins have a lot more to do on Xen, that I'm missing those aspects. All of which I'm sure can easily be integrated within Xen.