hi Bm,
for my experience on the B737, B777 & B744(B737's FMC being Smith and B777 & B744's FMC being Honeywell) they behave quite differently when you select extended centerline (which is, i believe, what most of us do when we are being radar-vectored).
for the B737, i noticed the vertical profile on your EHSI will be in gross error if you are heading AWAY from the CF. the FMC seems to calculate your current profile based on your current track (straight ahead) till the point of intercepting the inbound track, thus giving you a false sense of being low on profile. it would be quite accurate if you are heading TOWARDS the CF. to overcome this problem, i dont usually select extended centerline until i am approx on an inbound course.
whereas on the B777 & B744, when extended centerline is selected, the FMC assumes a great circle track from present position to the next fix (in this case, would be the CF) thus give you a rather accurate descent profile.
while i am writing this response, an idea pops into my head. i remember the B737 FMC also assumes a great circle track to the NEXT waypoint IF there is a DISCONTINUITY. as i am not on the B737 anymore, BmPilot, could you try this out and see if it give a more accurate profile as compared to an extended centerline??
any other B737 guys have any say?
HS