Wife and I ALWAYS try to bring a liter each from home or purchase at the duty free store in the departure/connecting airport. We are on island a lot, so it really saves a few bucks. You are correct in that the duty exemption is 1L per person for spirits, 4L of wine or a case of beer.

We purchase wine on the island, as the duty on it doesn't hurt you as bad as on liquor.

Beer is usually purchased at the brewery, since we head to Rum Point as well ($35 US a case). I happen to really enjoy CayLight in bottles, Cay Brew is solid as well. The Iron Shore Bok has tasted great (reminded me of Bass Ale) out of the tap at the brewery, but I never bought any.