Originally Posted by pgp
My biggest concern is sailing the best course to weather, speed seems to me the major component.

IMHO the best way to improve your upwind performance is to practice with another boat most similar to yours side by side and see who is quickest, make some changes if you are slower, and try again.
The gps will show your speed but you wont know if the number shown is "good" because of changing conditions like wind, current, waves etc.
It could be useful to download the data to a PC though, you can see your tacking angles and tack-to-tack speed.