Performing code review of tasks spanning several change sets

In RTC 4.0.1 we added a new view called the "Change Summary" view which is designed to handle a selection of change sets and show the user the aggregate of the changes (i.e the 'net effect' of those changes, mostly by comparing the first start state and final end state). In some cases, a selection of change sets may have an "Open With" --> "Change Summary" context menu action, otherwise the default open action may be the Change Summary view instead of the Change Explorer view (which is the case with change sets attached to work items)

The following blog post shows how to code review multiple change sets using the Change Summary view: Reviewing Code Changes with RTC

In RTC 6.0.1 a Code Review feature was added. This feature also supports reviewing multiple change sets, and offers a comparison of each file which aggregates the changes (shows the 'net effect').
See the following links on Code Review:
RTC 6.0.1 New & Noteworthy - Code Review
Using Code Review, Part 1
Using Code Review, Part 2

Assuming you're looking at the change sets from the work item, multi-select the change sets and open them. The Change Explorer will show all changes in the file view or group them by change set if you switch to change set view.

Multi-select also applies to change sets in Pending Changes if you want to open them in Change Explorer from there.

 See also Working with the code review tool.