We've chartered IP370s from IYC 4 times over the past 5 years, and ranged from the Spanish Virgins to St. Croix, to Anegada and just about everwhere in between in the USVI and BVI. The IP370 is not a sport boat, to be sure, but it is heavy and solid for its size and should be more comfortable than a Beneteau or Jenneau in the same size range when the wind picks up. As is the case with all IPs I've sailed (including the 35, 350, 380, 40, 420 models--over 80 days in all sailing IPs), the steering is stiff and takes effort. If you had the cutter rig--most are--you can have a hard time coming about if you are going slow and don't have the hang of getting the genoa through the slot between the forestay and inner headstay.
By comparison, our own boat is nimble and weatherly, but when we go on a charter, we are more interested in relaxing than racing. If you were looking for a race boat, your disappointment is understandable, but the Island Packets are not represented as such.
The boat is one thing, but I don't understand your disappointment with IYC. Could you elaborate?