The VCA-DT certification is the first step of a new path specific for Desktop Virtualization based on VMware products.
The official site is: http://mylearn.vmware.com/mgrReg/plan.cfm?plan=19733&ui=www_cert
On the official page there is the blueprint, but actually there is no link to the mock exam:
The exam will go live probably on April 22, and the beta period is finished.
My experience with the beta exam
I was lucky enough to get the invitation but also to find a day to take the exam (the beta period is usually very small with available dates).
Good news is that all VUE testing center can be used, so no much problem to find also a available place "near" me (this was not true with the VCP-DT beta, were I haven't found any available center under 350km of distance).
The exam was very similar to traditional VCP exam... only multiple choices with a similar difficult level.
A good memory on menu names and position could be required.
So I suggest to do not only study the official documents (http://www.vmware.com/support/pubs/view_pubs.html) but also test the products.
As the VCP3 and VCP4 exam, there are also question on specific functions... so use the blueprint to check your knowledge level and coverage.
A nice (but unofficial) study guide is also avaible now: http://damiankarlson.com/2011/02/02/vcap-dca-study-guide-now-available/
Some days ago I received the email with the exam results and I was really happy to see that I have passed the exam (to be honest I know to have make some mistakes on some questions due to few time for the preparation).