not me, but then i dont remember the last time i used the AC, mayb i should..
You should use aircon at least every week to ensure that the system is lubricated and the seals don't dry out. I use mine all the time to ensure this should never happen and the quality of the air within the passenger cabin remains the same, winter or summer. Any drop in power would be miniscule and not noticeable in day to day driving - it would only show up on dyno testing and the loss of economy (maybe 2-3 mpg) isn't worth worrying about for a performance car.
Believe me, having owned a Boxster for almost 4 years, you don't want to start having to replace parts of the air con system because the gas leaked out from somewhere. It won't be as simple as a recharge - there will be associated damage (condensors/dryer/pump/seals etc). Call it preventative maintenance, or else what's the point in having it on the car in the first place ? At least it's standard on the GTI and not an expensive option for the first purchaser.
Cass
