The last step of a long journey
I will start from the last step of the VCDX path, because I think that is the most interest and hardest part, but also the more distintive part.
As clearly documented in the application form (http://mylearn.vmware.com/register.cfm?course=67611) this final step is structured in two distinct phases:
the application and project submission
the inteview with the project defense
Those phases have also two different and specific fee.
Probably is also the more difficult part, as the pass rate is lower than 50%. How each part of the application and the interview compose the final result (that is only a pass or not pass) is not clear (for me), but I suppose that the application and the defense are the most important part.
Also I do not know if the results of Admin and Design exams are used to build the final results.
The application
When I done my application, there wasn't any information on how make it, only the information in the application form itself.
Now some good infos are available in the preparation guide: http://mylearn.vmware.com/register.cfm?course=72147
And also the Design Workshop V4 can help a lot, because you can use the material as a track of your design or as a way to do a review.
As written in the prep guide, the application process is similar to submitting a resume for a job.
It is composed by the application form (filled in all its parts) and a project, which could be real or fictitious, but must be realistic and “well designed”.
For VCDX3 is possible submit a vSphere design. I think that could be better submit a vSphere design, at least you can reuse it if you cannot complete the VCDX3 path and you go directly to the VCDX4 one.
About vSphere 4.0 or 4.1 I'm not sure, but I suppose that both could be fine... But just explain why you will choose one or the other...
I think that (IMHO) this is the hardest step of the entire VCDX path, because there isn’t a template on what you have to produce and there are only few information or suggestions about this part.
This is certainly the longer part (in term of required time), because at least 30-40 hours are required, but more are better and more are required for non english native people.
How many pages is not clear and is not specify at all… I found that some projects have a size between 100-250 pages, but I have no idea if it’s the right size. The content is more important! Also it must cover all the point of the applications and maybe more 
Mine was about 10 documents and about 150 pages... so not so big.
How many documents or files also is not specify, but I suggest to structure the documents in a clear and simple way, in a form similar as you would submit to a customer.
As written in the prep guide, mandatory VDCX documentation are:
Architectural design document with diagrams and blueprints
Implementation and next steps documentation
Validation/test plans
Operational plan/guide
Installation and configuration instructions
What about the language? If english is not your first language (as my case) try to keep the sentence simple and shot. And use a good spell and grammar checker 
Remember also to check that the names of technologies and products are written in the right way (for example: VMware and not Vmware!).
There is a template for your project? Not officially, but if you have access to Partner Network you can find some template for standard virtualization project. This could be a starting point… not for the content, but for the structure of your documents.
Some other hints? I'm under NDR, so I can't say more... But see VCDX Tips from VCDX 001 John Arrasjid: http://www.yellow-bricks.com/2009/10/01/vcdx-tips-from-vcdx-001-john-arrasjid/
This step does not require any travel and can be done also before other steps, you have only the deadline related to your defense sessions. Pay attention that when you receive the application's “invite” you will have probably not so much time until the deadline… So prepare your application before!
When you have finished the application you have only to send the zip file via email and wait…
There will be a first reply (if there is any formal problem in the application) and usually after 1-2 weeks there will be a first technical rewiev... if passed then you can go to the next and final step!
Note that if the application is accepted, this does not mean that is good enough to pass the defense... The application must be complete in each part... but I do not know people where the second review (the first is formal, the second is technical) was refused (but this does not mean that was never occured). So be very careful on this part... Be sure to submit a good application to be able to have a good defense on it!
