I often run studies that target speakers of a specific non-English language, and it's important that the study materials be in the target language. Localization in Gorilla is fairly good and has improved a lot, but there are a number of missing features. Two that come to mind are (a) localization of pop-up boxes (e.g. when a participant tries to proceed without giving an answer); (b) non-English spellcheckers (or at least the ability to disable the English spellchecker), etc.