Ok, new times:

```
Unit('dimensionless')

In [4]: %timeit float(q)
10000 loops, best of 3: 102 us per loop

u.dimensionless

In [4]: %timeit float(q)
10000 loops, best of 3: 66.3 us per loop

Unit(1)

In [4]: %timeit float(q)
10000 loops, best of 3: 80.8 us per loop
```

I'll therefore switch back to using u.dimensionless - thanks @eteq!