Little user study information is currently available relating to simple Dry Powder Inhaler (DPI) user interfaces, although it is known that ease of use is a factor in patient medication compliance. User studies that include devices with different numbers of steps required to prepare a dose are referenced and discussed. A particular issue of wasting doses, termed ‘over-compliance’, is reviewed. Vectura has undertaken user studies to explore how subjects perceive feedback from devices in which opening a cover also makes the dose ready for inhalation and compared the Vectura Open-Inhale-Close (OIC) device to the GSK Breo® Ellipta® (BE) device. This paper concludes that simple user interfaces with few steps can lead to fewer errors than interfaces with more steps. Over-compliance is investigated and it appears likely that it is due to patients judging the ‘click’ when opening the cover to be both the point at which the dose is ready to inhale, and also the point where the dose is committed (the point at which returning the cover results in indexing to the next dose). There is a region of rotation of the cover in BE where the dose is committed, but a ‘click’ has not yet occurred, therefore the user is unaware that a dose has been committed. The OIC device feedback is such that a click occurs close to the end of stroke, before which the cover may be returned to the closed state without wasting a dose, and after which the cover moves into the inhale position.