I know these kinds of responses aren't really popular but...
Why bother doing any of that? Why aren't you just using regular text fields (and any other applicable form field)? Why force the user to click yet another time to edit a field?
In my case I wanted my users (who have no idea the difference between a web or desktop application) to have the feel of an Excel spreadsheet. This is a table with around 30 columns and 12 or so rows. Putting three textfields in each of those table cells (requirement) would just look terrible, and make the table so large as to make it unusable.
So, I used Mike Tuupola's excellent jEditable plugin, and now I have essentially a web-based spreadsheet application, which looks and acts a lot like Excel. Click in a field, edit and hit "return" key, and your information is saved via an ajax call.
-- Josh
