Which Island Packet?
I think that the reason that people say that Island Packets are slow is right in your post.As you said, "The other day in 8 knots I was sailing on a close reach at half the wind speed."
To put that statement in perspective, the other day I was sailing on my 38 foot cruiser on a close reach in 8 knots of wind (true)and my speed was between 7.6 and 8 knots. My boat is only a moderately fast boat. Newer 38 foot designs owe me a bucket full of time.
More to the point, if you look at the PHRF ratings for a IP 380 it is 162 to 168 depending in region and setup. Putting that in perspective a Beneteau 38 rates 114, a Hunter 37-2 rates 120, a Catalina 38 rates 120, a Sabre 38-2 rates 117, in other words 40 to 50 seconds a mile faster. That is a lot when you consider that PHRF rating are based on predominant average windspeeds which tends to minimize the performance difference of boats. At higher and lower wind speeds the speed advantage of these other boats greatly increases.
I think that it valid to say that not all of us value speed equally and that in exchange for a lot less speed IP''s offer a lot of space and capacity for its sailing length. And that''s okay.