Well, I was initially interested in this restrictor to be able to play the light cycle stages in Tron correctly, but like you, I had reservations about being able to play other 8-way flight stick games. After reading Delusional's review, further back in this thread, I decided to go ahead and give it a try and so far, I must say that I'm pretty impressed and agree with Delusional's thoughts. It doesn't limit your ability to hit diagonals...it just doesn't make it quite as easy as it was with the stock restrictor, which is a good thing. Now so far, I've really only tested Tron, Gorf, Zaxxon and Mad Planets, but all of those have worked like a charm, diagonals and all!
I do need to test a few more trigger stick games, for variety, and I will report back on those, but so far, I'm very happy with the results.
Speaking of, isn't there a fairly definitive list of trigger stick games around here somewhere?