The question of whether to go straight downwind or tack downwind can be quantified if you have a gps, a bridal vane, and a hand held wind meter, and I have all 3. This can be put to rest very easily.
If you are on the water and want to know the wind speed, point your boat directly downwind according to your vane and check the wind meter. If it says 5 mph and the gps says 5 mph, adding them together gives the actual wind speed of 10 mph.
If you want to head off 45 degrees downwind, it will only pay in reduced time if your boat speed is greater than 7.1 mph. The longer distance is a product of the square root of 2, which is 1.414. Multiply 5 mph x 1.414 and you get 7.1 mph. Some cats will sail faster than this speed and some will not, but under these conditions, 7.1 mph is the magic number.
A Hobie 20 will absolutely beat that number. See page #7 here : http://static.hobiecat.com/2010_archive/support/pdfs/HobieU.pdf
My Wave is going to be a close call, and I an very interested in performing this experiment in a variety of wind speeds in order to see if any conditions are favorable. Whether the Wave will benefit is unknown to me at this time. I am hopeful that the addition of the jib and the traveler will make enough difference to merit their cost and make downwind tacks worthwhile, but I am betting it will be a close call.
I much prefer to actually do the experiment myself than to take the word of someone else regarding the outcome. Of course, you guys WILL take my word when I post the numbers later this year, won't you? :>)