According to domain name statistics provider Ipwalk, sign-ups for Office Live have boomed in the week since Microsoft removed its wait list for the beta service:
"Without that bottleneck, the number of users joining the Office Live beta has increased drastically. The number of domain names connected to the service has grown from 28,623 on April 5 to 43,169 on April 12, an increase of more than 14,000 domain names in just a week."
That's a surge of 50% in just one week, which represents either a lot of pent-up demand or an enormous level of interest in what Microsoft is providing. I suspect it's the former rather than the latter. The starting number is not that huge, and we don't know how many people were on the wait list and have suddenly now found they're able to get started with the service. (Users based outside the US still can't sign up though).
A whole lot more people would be signing up, of course, if Office Live really was an online version of Microsoft's Office suite, but as I've mentioned before, Whatever Office Live is, it ain't the Web Office. All the same, Microsoft has managed to attract huge numbers of users to several of its other Live services, so perhaps Office Live will still manage to keep adding domains at a rapid clip.
It's easy enough to see if it does. Ipwalk updates statistics daily at its Office Live watch page. You can even download the numbers in Excel format.
[Update: added April 13th @ 01:56 am] A TechWeb report makes the point that Office Live offers free domain registration, which of course appeals to the something-for-nothing brigade. That also means, however, that the service is operating as a loss-leader. Will Microsoft make its money back?