Flowers was initially perceived as a mere cash-in, but as time wore on it has come to be regarded as a necessary listening stop in the Stones chronology despite the fact much of it revisits territory from the previous few records.
The Stones did the reverse of the Beatles in '67 - whereas the Fab Four put out Sgt. Pepper and followed it up with the odds-and-ends deal that was the Magical Mystery Tour - the Stones mish-mash record came first (at least Stateside), and they followed it up with their big 1967 psychedelic record, towards the end of that fateful year.
Whether that was intentional or not, Flowers is a record filled with so many entertaining tunes that, I even raised the rating of "Lady Jane" a half point, because it fits better with the flow of this record than it does with Aftermath! I mean, really, compare this with the previous effort and let's be honest - a lot of the tunes on Between the Buttons were half-cocked and disjointed in comparison.
Furthermore, Flowers succinctly sums up the 1966-67 era of the Stones and serves as a great lead-in for what would be one of the most controversial records in their career, and a real turning point.