[Gibbon1]

I think the answer is the discontinuity you get from a sharp bend is smaller than the highest frequency/wavelength in the signal. So you don't get any reflections off it. The way I think is the length of the wave front heading down the trace is much longer than the size of the bend. I think very high speed stuff can start having trouble with via's.

I think curved traces were used make layout easier when running tape. Bending the tape is easier than doing a cut to shift the trace over.

And safer, a problem with old tape layouts is it's easy enough to knock off a small section of tape. Old draftsman I worked with would check the layout against a blue print on a light table to make sure nothing was amiss before making mods. He also got really antsy if anyone was rummaging around in the drawers holding PCB layouts.

[davrosthedalek]

High speed designs definitely do not like corners, especially fast serial interconnects are often problematic (they tend to have really high clocks), think PCIe, USB3,...