I would offer that keeping vars as strings, even when using adapter services, is the way to go. The one exceptions may be dates, where converting to/from a java.util.Date type may be more easily managed than strings following a particular format (though that can be effective too). The adapter will manage the conversions for you. The only time I ever convert to types other than strings is when calculations are needed.
P.S. Avoid the use of float/double for dollar values. Using those data types can lead to accuracy errors.