To date, there have been several attempts made to build a database of normative data for English idiomatic expressions (e.g., Libben & Titone, 2008; Titone & Connine, 1994), however, there has been some discussion in the literature as to the validity and reliability of the data obtained, particularly for decomposability ratings. Our work aimed to address these issues by looking at ratings from native and non-native speakers and to extend the deeper investigation and analysis of decomposability to other aspects of idiomatic expressions, namely familiarly, meaning and literality. Poor reliability was observed on all types of ratings, suggesting that rather than decomposability being a special case, individual variability plays a large role in how participants rate idiomatic phrases in general. Ratings from native and non-native speakers were positively correlated and an analysis of covariance found that once familiarity with an idiom was accounted for, most of the differences between native and non-native ratings were not significant. Overall, the results suggest that individual experience with idioms plays an important role in how they are perceived and this should be taken into account when selecting stimuli for experimental studies. Furthermore, the results are suggestive of the inability of speakers to inhibit the figurative meanings for idioms that they are highly familiar with.