heya charlie,
sorry man, not meaning to give you a hard time... but honestly, i wouldnt have said it if i didnt test it extensivly.
im pretty critical on control issues and feel... so my awareness of the controller situation may be higher than most who are paying a bit more attention to the actual game playing.
if you play a real starwars yoke side by side with a completely vertical - it will be pretty crystal.
i thought of one thing that could be altering the way you feel about the slant is that the y axis travel you have is shorter than the one i designed... thus the impact on your wrist isnt as bad as mine is.
however, even with that in mind i still feel the slants do make for a lot more comfort as well as making it easier to handle on the x axis.
most arcade controllers are designed and built a certain way because of specific needs as well as having tons of prototyping and testing before the final product is produced.
atari was one of the most innovative (imop) as far as control designs go. race drivins sitdown controls are bar none the best driving controls made ever for instance.. so those two things alone should say something about thier choice to slant the controller grips.
As for tatsumi... well, i love TX-1 (tatsumi design -distributed by atari) ... however, that company hardly compared to the success and duration of atari.