There's nothing in CloudStack to track that so we cannot be definitive. But, it can't be many. We have seen few questions about its usage and integration. And OVM's share of the server virtualization market is quite low. Given limited user impact, if this is really the only problem I'd defer the fix.
From: John Kinsella [mailto:jl...@stratosec.co]
Sent: Thursday, October 18, 2012 10:04 AM
Subject: Re: Drop OVM in 4.0?
Do we have any idea how many CS users use OVM?
I suspect I know the answer to that...so, do we want to consider adding
(optional) code in the future to phone home with some usage stats?