I am not sure if there is any construction going on at the hotel at the hotel, however, I do know that the resort's Aruba and Bonnaire towers have already been renovated. I would recommend joining the Holiday Inn's Priority Club and e-mailing the hotel a week before you arrive to request a room upgrade and a room in either the Aruba or Bonnaire Towers (they have accomodated my request the last two times that I have been there).
The service is fine at the Holiday Inn. The food at the a la carte restaurants (good but not excellent) is better than that found on the buffet (OK to good but not bad by any means). The AI option is well worth it given the cost of food/drinks at the resort/around Aruba. I find those that are unhappy with the food/drinks at the resort are the one's that are not on the AI plan (i.e. they feel they did not get value for their meal/drink - e.g. $4.50 for a dixie cup of draft beer is excessive for those not on the AI plan, but it doesn't bother those on the AI plan).
As for the mixed reviews of the hotel, the Holiday Inn is by no means a 5-star hotel (it is more like a 3.5 - 4-star hotel). That being said, the Holiday Inn (i.e. with the AI option) is about half the price of some of the other fancier hotels on Palm Beach with no AI option (e.g. the Hyatt). The hotel is also clean and on a nice stretch of beach. For the money, I find it to be the best value on Palm Beach/in Aruba.