I am surprised at the negative reviews. I stayed for a week recently (over EDC weekend) and the service, cleanliness, Margaritaville, Go Pool, and activities on site were all impeccable. The price you pay for the Flamingo is far less than the adjacent properties (Caesars Palace, etc) and you can easily walk over to those other high end casinos. The GO Pool was a lot of fun, as was Margaritaville. Flamingo has a more casual feel to it then some of the other casinos which was a positive for me.
The only negative for me was the check in line---it was awfully long and the self check in kiosk didnt work for me.