Formula passes syntax check but generates all null values

Solved my own problem. After fooling around some more I discovered I needed to remove the single quotes around the rating numbers since they are really numbers, and not just text. Using this:

if field('appraisalRating') == 1 then 'Does not meet expectations' elsif field('appraisalRating') == 2 then 'Needs improvement' elsif field('appraisalRating') == 3 then 'Fully meets expectations' elsif field('appraisalRating') == 4 then 'Exceeds performance expectations' elsif field('appraisalRating') == 5 then 'Significantly exceeds expectations' end

works perfectly. Derp.