Struggles with Managing Agile Projects Remotely

This is basically a call to respond.  I'm going to be creating a survey soon on the issues that project managers face when managing agile projects remotely.  However, I'd like to hear from my readers now on their thoughts on this topic.  

Have you managed an agile project remotely?  Have you utilized a completely or mostly geographically dispersed team on an agile project? What struggles did you face?  What failures did you encounter?  Was it more difficult than managing a waterfall project remotely?  How and why? 

Not much has been written on this topic so I'm looking forward to your responses.  Thanks in advance!