Overall, on a happiness scale of 1 to 10 who fares the best in terms of achievement? 

It's not the 10's. Be an 8:

Via Happiness: Unlocking the Mysteries of Psychological Wealth:

When individuals complete happiness surveys that use a 1 to 10 scale, those scoring around an 8 often tend to fare the best in achievement. Why might the 8s of the world outperform their friends and neighbors who are 9 or 10s? It could be that 8s benefit from the creativity and energy of happiness, but also maintain a touch of worry that helps to motivate them… Similar results can be found in an analysis of a huge sample by Shigehiro Oishi, who analyzed the satisfaction scores of over 100,000 respondents from all over the world. Those who scored well on happiness – the 7s, 8s, and 9s on a 10-point scale — had higher incomes and more advanced educations than both the 10s and those who were unhappy.

What about those of us that refuse the construct?

There is no way to happiness. Happiness is the way. 

I'm with Mark... it could also be that a 10 point scale is pretty much experiential bullshit.

Really, can anyone honestly feel a precise difference between 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 that is consistently reportable from day to day, week to week and year to year...?  

Yeah, I'm going with an 8, because simple taking this test feels like a 3...