Flo Rida is the master of turning fleeting gimmickry into full-length tracks, which is perhaps not as good as mastering musicianship but good enough to get him charting, year after year. Normally, though, his gimmicks are timely: recruiting T-Pain in his getting Ke$ha on a hook before she became Ke$ha, recruiting David Guetta (as a producer) or Avicii (as a sprawling sample) just as EDM became a household acronym. The titles usually give them away a bit, too; "Right Round" can only be preceded by "you spin my head...", "Good Feeling" by "Ohhhhhh, sometimes I get a...." This means that with a Flo track called Whistle, you can guess the gimmick almost immediately. You can probably also guess what Flo does with the word. But if not, the first few seconds will make it clear:
The gimmick here, as you've probably guessed, is a whistled hook. This is a problem. Whistling was last year's trend, and a certain pair of Jagger-movers made it overplayed. Whistling the melody to "Just Can't Get Enough" is not an improvement. Nor is pairing it with a double-entendre ripped off near-verbatim from Lauren Bacall--a metaphor ruined by being made more explicit. Flo's obvious enough to taunt "blow my whistle, baby," but his quoted instructions would not literally work. "Whistle while you work it," later, might have worked--it's a snowclone just stupid enough to stick as a hook--but Flo smothers it in a bunch of Flo Rida delivery.
There's the real problem, and it's probably inevitable: between the guitar mess and chorus comedown, "Whistle" wants to be something like a Gym Class Heroes or Maroon 5 track. But both those groups use hook singers: Adam Levine, Neon Hitch, Bruno Mars. Flo's just got himself, and he can't make the verses more than throwaways or deliver a chorus that probably wouldn't even work without him. He doesn't have a sample, either, to steal the show. He's just got his anonymous self and that whistle. "Moves Like Jagger" had a very similar whistle, and a month in, its (very similar) whistle sample stopped sounding catchy and started to sound mocking. "Whistle" already does.