RE: best allround wavesail on the market?
A 2.7 kg 5.5 wave sail: If all else was the same, it would feel great. However, getting a sail that light means using very light materials and since sail cloth character decides a lot of the feel in the sail, I think it is hard to build it with the same feel as a "normal" sail. So in practice, the answer on the question "would it be good" would be "it depends".
The lightest sails I ever had was my 2001 Hot Psyclone. I think the 5.3 was just under 3 kilos. It was a really nice sail which also survided lots lots of chrashes in mast high Maui waves. Compared to the current heavier sails, the cloth was thinner, the mast pocket was not nearly as strong (ie got tore by broken masts, reef etc) and lots of other details was also more simplistic. Overall, I think the current models are better sails, despite weighting 600-800 grams more.