In general, having metadata about the fields (names, validation rules, ability to convert to/from XML/JSON) are all really valuable... if not now, next week. The extra indirection of having this data around has never failed to be useful on any project I've worked on.
The costs of the extra data are: performance (nothing you have to worry about, but is causing some GC issues with the Foursquare guys) and a little more learning. But you will ultimately need some of what Record (or Mapper) offers in terms of field metadata, so you can either implement a partial solution or use what exists (and enhance it because you're a committer).