You may enjoy Flag because: It's different. There is always something interesting about watching an anime that makes an effort to step outside the box, even in cases where it's not 100% successful at what it's trying to do, and Flag is definitely worth checking out on that basis. Firstly, it's a title grounded in a real-world feel, which is uncommon enough in anime to be worthy of note for that alone. Everything from the character designs to the color palette to the presentation of the military heirarchy is very naturalistic and modern-day. Even the obligatory mechs are presented more like advanced tanks than the gravity-defying super-weapons that are the norm.
Beyond that, there is the show's most notable feature: the way in which the entire story is delivered as seen through a camera lens, supplemented with still snapshots and computer graphics, as though being put together as a documentary after-the-fact. This could easily have been an irritating gimmick, but I found it to be one of the series' biggest strengths. It is fascinating how they manage to give a sense of getting to know the woman "holding" the camera through the moments she captures - the way the camera always lingers on a particular person, the moments she chooses to focus on, etc. It's really quite impressive how immersive it all becomes. There are some shots where something about the colors of a sunset, or the sharpness of a helicopter lifting off against a cloudless blue sky had me blinking a bit at how it had managed to convince my brain that it was seeing a live-action moment, not something animated. Very impressive.
You may dislike Flag because: It's... kinda boring, unfortunately. This is especially true in segments where the story shifts from following the camerawoman described above to a second journalist following rising tensions in a metropolitan area. The entire purpose of his plotline seems to be to give the viewer a primer on the religious and political backdrop of this fictional Middle Eastern country... and there were long stretches of time where his droning on and on made me feel like I was watching a fifth-grade filmstrip presentation, rather than anything meant to entertain. The information was necessary to give weight to the rest of the story, but the info-dump-y nature of the delivery did nothing to make the viewer really *care* about the fate of this nation.
Bottom Line: If you're a viewer who likes anime that tries something a little different, or takes on weightier issues, Flag is worth a look... but be prepared for it to be a bit of a slog at times.