3 months ago I complained that star ratings were dropped from iOS, but as of 10.2, they're back. More or less... you have to explicitly enable them by going to Settings | Music and toggling "Show Star Ratings" (Mystery: why doesn't Settings' find box show anything for "star"? Their search tool is ridiculously limited...)
Once you're there, this option gets added to the "..." menu when a song is playing...
Then it's a pretty simple dialog:
It's distinctly tougher to get to than previously, where tapping on the album cover image would flip the image, and then another tap would set the # of stars and flip it back with no need to hit "Done". People were complaining about the complexity on MacRumors, since setting a star rating used to feel like a more or less reasonable thing to do while driving, and now it's a bit on the fiddly side for that. Overall I think it supports my earlier speculation that Apple's UX folks felt there was too much confusion relative to overlap with the heart-based Like/Dislike options, which feed back into Apples "music selected for you" AI in a way the stars don't - so they'll keep stars around for power users, but for most folks they want to keep them on the simpler pattern.
It's reassuring to see Apple is aware that this is an important features for some of their users. (The earlier hack of using Siri to set the star rating, besides interrupting the playing song, wasn't complete for me because I often I just want to check if I had already advanced a song to the 4- or 5-star level, and Siri wouldn't tell me what a song was already rated) Hopefully this should ensure stars in iTunes will remain for the foreseeable future. (Critical to me because of my use of smart playlists)