The Lightning Conductor Web Part has been improved to offer a better performing treeview control. Customers with thousands of Site Collections experienced a delay and in extreme cases a timeout. Rather than trying to build the treeview of the Web Application in one go, the treeview now loads on demand.
Loading the treeview on demand means that the objects such as sites and lists within the site collections are only loaded when that branch is expanded.
With this new treeview control you will be able to aggregate (rollup) from across multiple site collections without timeout issues or performance lags.
The web part trial can be downloaded from: http://www.lightningtools.com/pages/lightning-conductor-web-part.aspx