Coming very soon, we're going to be offering free IE7 tests - no registration required. We've got a new screenshotting system that Matt's built, which gives us much more capacity than we currently have. The IE7 tests will be running on this new system from the start, and we'll be transitioning all the other browsers to it shortly after.
This is the first in a whole raft of changes and upgrades we're making to the SiteVista service over the coming months. We'll keep you posted!
Update: We have hit some delays in getting this new system live and have decided to rework most of the codebase - but keep watching the blog for new updates towards the end of this year/beginning on next year as we build up to some even more exciting features and updates.