Cost
I find the price is still pretty high : even for the Foundation version, that's still at least $1k per server. For most basic servers, that's still a 30% to 50% price increase if you decide to go virtual.
VMware has announced three new VMware Infrastructure packages that are designed to help IT administrators at SMBs make the decision to deploy virtual infrastructure. The SMB bundles are based on the latest release of VMware Infrastructure, which will include the new VMware ESX Server 3.5 and VirtualCenter 2.5, and are focused …
VMWare is not well-liked by the channel. Citrix has a real opportunity here on both price and performance with their Xen-based products. SMB is not a risk-adverse as large enterprises.
Old-school companies will continue to buy 1st generation virtualization, but the more nimble smaller companies already know and trust Citrix.