I often talk with Citrix customers who are interested in virtualizing XenApp ( Presentation Server ) based on the potential to consolidate servers, increase flexibility or enable new HA/DR capabilities. However, a frequent comment I hear is that we tried this before with ESX but the overhead penatly was to high so we are still running XenApp fully installed. This may have been the case before but things have changed, now it is possble to get the benefits of Virtualization by runing XenApp on XenServer 5 without the downside you may be concerned about.
If you would like learn more and engage with the experts without traveling to an event, make sure you register for the Citrix Delivery Center Live event on Devember 4th. You can register here and check out the other topics that may be of interest as well.