I agree that short shifters don't destroy transmissions by themselves (well, in that case nothing actually ruins your car by itself, right?). But there are a few reasons why I don't really care for short shifters. Firstly, installing and having a short shifter encourages more aggressive and sloppy shifting, and there's a small period of time where you have to get used to it. Secondly, there's absolutely no benefit to be gained in city driving, and if you do participate in motorsports (like SCCA Solo II or whatnot) then there is much more room for improvement in your driving technique that needs to occur before you will be able to trully reap the benefits of slightly quicker shifting. Plus, after all, short shifters are somewhat annoying to install.