I am curious about what other users do about the segmented circles and arcs? I find this really inconvenient - I tend to forget to set the segment count to a high number, consequently intersections are not accurate, and eventually Sketchup loses the circle entity information. This is the biggest reason preventing me from switching to Sketchup for all my drafting.
Incidentally, if anyone is interested, I figured the number of segments n required to limit the error f (maximum offset between true circle and segmented circle) is given by n = pi x sqrt (r/(2f)). For a maximum error of 1/16 in. this comes out to 2pi sqrt D, D in [in].