I've found it handy to do things like divide paid traffic into specific channels, such as paid keywords and CSE traffic, using referral path as a dimension. This seems to work well, as these sites normally wouldn't send traffic to my sites, unless I've hired them to do so. Another idea is correlating specific dimensions to site goals.
The drag and drop Advanced Segment Creator is very simple to use. You're able to select from many dimensions and many metrics and use 'and' and 'or' logic.
Google slates this addition as an "enterprise-class feature". I tend to agree and think that steps like this will bring Google closer and closer to solutions like Omniture. Go Google!