I made the jump to DX8 and am sad I did. Here's what happens:
I have P933 with a GEForce 2 GTS running Detenator 3 drivers. I should have held for Det 4 drivers to work with DX8.
Now, I often get the planes disappearing when diving on them and a strange "diagonal wipe" effect, where the screen redraws and the cockpit shows slightly overlapping versions of itself and it corrects itself diagonally drawing from right to left.
These weren't issues pre-DX8 at ALL. They completely conincide with installing DX8.
Caveat emptor.
X2