Thanks to Robert Bruckner's blog, I've learned that the Report Builder 2.0 (previously known as Report Designer Preview) Release Candidate 1 is available for download. This should be a feature-complete build of Report Builder 2.0, which is scheduled for official release in October.

IMO, Report Builder 2.0 is one of most exciting features of Reporting Services. I expect it to blur the "great divide" between standard and ad-hoc reporting. Based on some preliminary feedback from our business customers, they are very excited about Report Builder 2.0 and they favor it instead of Report Builder 1.0. Despite the unfortunate name, Report Builder 2.0 has very little to do with its predecessor. Instead, it's very close (almost identical) to the BIDS Report Designer as it supports the full RDL feature set.

You should definately evaluate Report Builder 2.0 for ad hoc business reporting.