We've improved Webmaster Central's robots.txt analysis tool to recognize sitemap declarations and relative urls. Earlier versions weren't aware of sitemaps at all, and understood only absolute URLs...Reporting is better, too. You'll now be told of multiple problems per line if they exist, unlike earlier versions which only reported the first problem encountered...

Webmaster Central Official Blog [googlewebmastercentral.blogspot.com]

The blog post also mentions Google's new support for the X-Robots-Tag [webmasterworld.com] we covered in July.