Basically the two requirements are: VCP4 and VCA4-DT certifications... no course is mandatory, but only recommended.
Sound strange, but I've not found the offical price of this exam. In the web site there is only this sentece "Register for the VCP4-DT exam before September 1, 2011 and take advantage of the $50 discount."
So I have to assume that the price that I get from VUE site is already the dicounted price. If it's true... then the exam costs more than the VCP4 exam!
This mean a "delay", first because you pass one exam, but you get the # only several weeks later, second because you require the authorization and you have to wait.
Note that you may be authorized on VUE site before you get the confirmation email from VMware (in my case I've got the email one week later the real authorization, that was quite faster).
Second "problem" is that this exam is limited to only some VUE testing center (like the VCAP exams)... In my Country this is a big limit because there is only one enabled testing center (thanks that it exist, because some months there was no testing center).
Exam length is documented well in the blueprint: 70 exam questions in 90 minutes... IMHO the duration is fine... I've got 30min of extra time (because English is not my native language) but I've finished in 90min.
Note about the extra time: it is granted automatically during your exam schedule by the VUE site. So check in your confirmation email to see if you get it.
Exam is different from VCA-DT, especially in arguments coverage. Most questions are multi-choice, a couple drag-and-fit (like some of VCAP-DCD) and in most case they are not mnemonic, but require a little of reasoning.
But some nmemonic questions still exist... A few also on the command syntax (IMHO I hate this kind of questions, but I understand that could be necessary to make numbers)
But first surprise was that it was based on View 4.6(with a couple of question specific on View 4.6)... not on 4.5 like VCA-DT (to be honest it was a generic 4.5/4.6 exam).
The blueprint is not too much clear about this (it talks about a generic View 4.x) and I've study on 4.5 docs
About the difficult it is higher than the VCA-DT exam... I've passed, but to be honest I was not sure to pass: in the first pass I've marked about 60 questions to be review...
About the arguments, some (in my test) were very "popular" (and not the one that I was expected...)
Do not assume that there is a equal distribution of arguments!
In my case, also some arguments were totally not present at all (of course I cannot say which arguments...)... Maybe this could depend on how the questions set has generated?!
I think also that a question was wrong due due an error in a word (I've put a comment in the question)... Other need to be read more than one time to understand what is required.