I put one on my modular cabinet - there is absolutely no substitute for the 4 way dedicated diagonal mount for these games. Even a cheap 4 way on the 45 degree mount is better than the alternatives.
At risk of starting a flame war here, what alternatives have you personally tested?
There is no difference in the SHAPE of the restrictor plates between a straight mounted 8-way (provided it is not a Wico stick, which doesn't have corners--or a Super, which has soft corners), and a turned 4-way.
This leaves stick throw and overall feel as the only two variables.
For stick throw, my T-stiks in 8-way mode have a 3/16" each way throw (3/8" total), vs. the 3/4" total for both my Wico and my Pacman stick.
I will give you that the turned 4-way is much preferable to an 8-way Ultimate, Competition, or Super.
All those sticks have REALLY long throws to get to the diagonals, and the corners on the Super are "soft", as I mentioned earlier.
I put foam tape on my Comps to stop the stick as soon as it depresses the button, and still get 1"+ total throw on them corner-to-corner.
With regard to feel (which is a very subjective thing), I much prefer the feel of the T-stiks for games that require precise moves in a given direction, like Q*Bert.
They go from center to a given direction much quicker, and are wonderful when you try to reverse directions quickly because they don't have to travel as far.
As far as an 8-way stick not feeling the same as a turned 4-way, everybody who thinks that needs to try a T-stik Plus.
If you close your eyes, and pull the stick in circles--you get a perfect square.
This is the same perfect square you get with a rotated 4-way.
The other big advantage to the T-stik is that you can actually have THREE sticks in the same spot (an 8-way, a 4-way, and a rotated 4-way), all with the same stick.
My modular system has been all about perfect emulation of the original controls, but from a player's standpoint.
The T-stik PLAYS much better for me than any rotated 4-way I've tried, so the 4-way I was going to use as a dedicated 45 stick is sitting unopened in my pile.