So first of all, I signed up awhile back, because I thought it was cool, and I like to participate in beta testing.
And sometimes when you apply to participate in a beta test you get accepted, and sometimes you don't. After all, the product is in beta, so I just go in wishfully thinking, and don't get overly excited until I get the actual invitation. And I never hold my breath.
In fact in the case of Office Live Workspace, I just kept the email in a labeled area of my gmail account (yep, gmail; doesn't look like the OLW team is discriminating either for or against gmail / hotmail users), and then just plain forgot about it. Since I wasn't thinking about it, that's when the invite arrived -- gotta be some cause and effect mojo going on, huh?
But if you just gotta have it, and gotta have it now (and frankly, I like it so much, I can understand why you'd feel that way), here's my suggestion, which comes right out of an actual user experience: find someone you know who uses it, and ask them to let you borrow a piece of theirs while you're waiting for your welcome invite.
In our case, I have created several workspaces for team collaboration -- and a couple of them I have virtually turned over to a different member of the team to manage.
Now, they can't create authors (I still have to do that). And they can't create new workspaces (I still have to do that, too). And they can't delete documents. And they can't keep anything secret from me; I'm the workspace owner after all (hey, I'm not suggesting this is the perfect solution; it's just a solution, and it does work). But, they can do pretty much everything else.
They can upload documents, edit documents -- hey, if they wanted to keep generic Excel workbooks or Word docs, they could add and delete tabs and chapters to their heart's content, and never have to ever again ask me to delete a document.
The only limitation is filespace. So for that reason, don't ask me to loan you a piece of our workspace; it's not going to happen. Unless I already know you. Then I might consider it. Anyway, for our team members now patiently waiting for their own accounts, this is a great interim solution.