Si,
Field name usage for bibliographic data is also a "live" problem for me.
I've recently gravitated toward approaching the title field with author-date brevity, as is used in interlinear citation: Beauvoir 1962 (or Beauvoir 1962b in the rare case of multiple sources published from same year).
This pattern is easy to type, not terribly difficult to remember, and generally steers clear of confusion for my purposes.
On the other hand, if you like using the off-the-shelf sidebar search function (as I do, especially if I publish for students), that may give you a reason to stick with a longer concatenation: if the title field holds Beauvoir, Ethics of Ambiguity (1962) you can always easily find it even if you only remember that the source has "ambiguity" in it. ;)
Either way, then I end up modifying various templates (including the sidebar tabs) to show the caption field. Usually this will hold a version of the author surname plus full primary title (omitting subtitle), *but* I have the freedom to custom-abbreviate titles that are inconveniently long. It's convenient to build filters that fetch one field value *if* it exists, and to pull from a default field if not.)
It's awkward that the fieldname "title" is not really workable for the full title of the bibliographic source, since I like to use intuitive field names. Using fieldnames like bibtex-title bibtex-year (etc) works ok when field names are all hidden under the hood and handled through automated imports and forms, etc. But they're a nuisance to type repeatedly, and (worse for my purposes) they are bulky, and this becomes a problem in dynamic tables (which auto-sizes columns so that the bibtex-year column is twice as wide as the data needs).
I actually wonder whether there already is -- or could be -- something like an efficient sub-forum for people who are using TiddlyWiki in an extensive way for bibliographic purposes. It's not always easy to go searching through the google groups for relevant past posts, and I know there have been a ton of them. There's great benefit to converging on conventions together, since that way plugins, specialized ViewTemplates, macros (etc.) can be shared easily.
-Springer