As an admin of a cluster, I would want to be able to use external tools/apps for things like querying the database or adding users in bulk like I can do with the open source version. Will that kind of thing be possible?

We plan having tools to create sites and users by cluster admins. CSV import of users would be one of those. The easiest way to automatically create accounts for all your customers: download CSV template, open in Excel for example, paste data from other database, export to CSV again, load it to Wikidot, wait 5 minutes and have your users created (and maybe even mailed their new passwords, unless you supply them in CSV).

Being able to isolate and better "brand" a collection of sites has great appeal to me for use in our business. Even though I've been very happy with WDOS at work for a few years now, it's been frustrating that it's lagging so far behind the current Wikidot feature set. If clusters become a reality, is it safe to assume that the update process for new features will be relatively easy and painless?

Wikidot OS mistake was that it's a separate project. Based on the original code, but forked and not synchronized. We plan adding the cluster features to Wikidot code, the one that Wikidot.com runs, so everything possible at Wikidot.com would be instantly possible to clusters. Bugfixes included. You can simply think of everything Wikidot.com is now as just one of many clusters — probably the biggest one though ;-) — in the future.

Our plan is to get this working as soon as possible without any "added features" and then to gradually add features like the above-mentioned central users management, cluster configuration and other useful things. We do believe educational institutions are a typical use-case for wiki clusters (the other one would be companies' wiki space, think farm of the following sites: official company site, workers' blogs, customer relationship sites, internal issue tracker, knowledge database and a support site).

Also, WikidotOS?

OS = open source… not operating system ;-)

I think an answer to one of Ed's questions fits yours as well:

Wikidot OS mistake was that it's a separate project. Based on the original code, but forked and not synchronized. We plan adding the cluster features to Wikidot code, the one that Wikidot.com runs, so everything possible at Wikidot.com would be instantly possible to clusters. Bugfixes included. You can simply think of everything Wikidot.com is now as just one of many clusters — probably the biggest one though ;-) — in the future.

Added features: at first, clusters would be just the matter of isolation from other Wikidot.com sites (no fancy cross-site features added). Cross-site features may be added later (they could be enabled on per-cluster settings, cause due to security issues, they don't really make sense at current sites on wikidot.com).

Convert to cluster: we do plan having feature to "get chosen sites and convert them to wiki cluster". Users and sites would be cloned. Old sites would become redirects to new ones on the cluster.