From where can preorder customers download the latest Betas?

It seems that there are more recent versions than the initial Beta 7 around but neither the Beta download page nor the update function in the editor offer those.

The eMail sent out by Unity on 22.8.2012 said:

:
This is the first in a series of high-quality Unity Pro 4.0 pre-order beta releases for customers who pre-ordered Unity Pro 4.The Unity Pro 4.0 pre-order beta provides an opportunity to explore the new features and updates-in-progress, and give feedback about any problems you experience. The final version of Unity Pro 4.0 will be released at a later date.
:

So, where is the information about how to access them or aren't all Betas meant to be offered?

 

Buhhh!

 

did you check this thread? It is the top thread from "Forum>Developer Preview>Announcements: Unity 4.0 Pre-Order Beta Released"

It has the 4.0.0Beta download links.

 

There are two levels of Betas: one for folk that are 'tight' with the dev crew at Unity and will give newly integrated things a work out and the rest of us: when we get a beta you can call it rather stable and fodder to keep us quiet. And for any major problems in a beta they will iterate through a series of minor betas to resolve those before wide release in a beta or RC again.

 

I think the newest beta is Beta10, so i hope we will get a new public beta out soon...