I use a variety of rubrics in my rhetoric classes, mainly because my assignments don't lend themselves to the same rubric. For memorized recitations, for example, I use a four point rubric that assesses accuracy of words, accuracy of diction, accuracy of pacing, and consistency of interpretation (weighted equally, unless I want them to focus on one aspect in particular). For essays I usually use a modified version of the five virtues of style (Correctness, or conventional word choice and grammar; clarity, or clear meaning through word choice and syntax; vividness, or quality of imagery, figures, and use of active verbs; decorum; or ideas and tone suited to the occasion of the essay prompt; and ornateness, or appropriate level of style--not too low or too high for the occasion).
I should probably share my rubrics with students more often than I do. With oral recitations I do a lot of sharing, because I want them to be better at self assessment, but I don't tend to put in the extra work necessary to teach them how to use the essay rubrics (a flaw of mine, I admit).
In general I also think that the more weighty the task, the more detailed should be the rubric. It is not only helpful to the student, who can then see all of the expectations clearly and up front (with the opportunity to ask clarifying questions), but it is a safeguard to the teacher, who has multiple points of analysis to ensure that factors aren't forgotten or fudged due to human limitations of evaluating a single product.
On that last note, it also seems valuable to use long-term evaluative rubrics that allow students (and teachers) to see progress over the course of time. Using the same assignment multiple times with the same rubric works very well when assessing skills (whether speaking or writing skills; or skills of analysis, such as historiography or literary criticism).