I have both the 35-105 f3.5 and the 35-70 f3.5-4.5 mentioned above. For serious work, I would go to the 35-105 (or the 50mm f1.4 ), but it is a fairly significant handful size and weight-wise. For traveling light -- vacation and casual shooting -- the 35-70 is quite nice. If you start doing tests with grids and such, it does have more distortion, but it is small and light, about the same bulk as the 50 mm 1.4.

And we are spoiled today -- 2:1 zoom range is plenty for minor compositional adjustments (he says with a curmudgeonly wink).