This year, that changes. Apple has released a public beta of iOS 9 to anyone who wants to try it out, no strings attached. This preview is for people who want to know what they're getting before they install the beta, and for people who want to know what's coming without putting work-in-progress software on their own phones.
This preview will skip many of the lower-level things we normally cover in our iOS reviews including performance, battery life, general stability, and the amount of storage space used, as well as some security features and new APIs. Many of these things are subject to change as the software becomes more mature, so we'll pay thorough attention to them in the full review this fall.