Al mentions all the relevant portions of XenServer 4.0.1. installation, management, storage repositories, networking, templates, logs and reporting. Al though Al states this is very brief review, one is able to tell that across basically all of the aforementioned areas Xen seems to lack (some) enterprise functionality.

Like I said earlier, I was impressed with product during the training. As I gathered more information, I started see design questions that may lead the client or my design for a client down a XenServer path (or away from it for that matter). And that is what really matters most. Making proper technology decisions for a client that meets their technology and business needs. No questions on that one. Citrix has a lot of work ahead of itself and VMware has a pretty good jump on them. There is room for many players in this market, but I don't see companies planning on buying multiple virtualization products.  Clients are looking to standardize on one platform, get their people trained, and then findings ways to optimize. Adding an additional technology means there better be a darn good reason for it.

Read Al's review here.