Hello 2ND2N01,
This is the real test: Can you feel your car change speed at the moment that you shift? The ideal shift can only be heard, but not felt. Now, when shifting, you will feel the car surge when you get on/off the gas, right before or after the shift (depending on the direction), but the gear change itself should NEVER be felt---only heard. In other words, the car should not change speed in the slightest as the clutch goes up or down.
The only way that I know how to shift my car like this is to actually give gas while shifting to match revolutions, but this is somewhat fustrating to learn, and very rare, in that most people just do not care. (You can easily learn how to do this, but it takes time.) Also, the down-shifting version (the double-clutching with gas blipping) is hard on the gas knee, so I'm not sure that I can really recommend it. Furthermore, while I have yet to replace a clutch in one of my older cars, I only have 5k miles on my M5, so for all I know, I'm about to smoke my clutch!
So, I was wondering if you wanted to try shifting like the typical driver does, as this should be "good enough" for the car to behave itself for a while, and hopefully the smell will go away. So, perhaps you can try this, which seems to me to be typical:
1. GET YOUR FOOT OFF THE GAS BEFORE YOU EVEN THINK OF TOUCHING THE CLUTCH IN ANY GEAR EXCEPT FOR FIRST.
2. NEVER PRESS THE CLUTCH IN PART-WAY, OR EVER LET YOUR FOOT REST UPON IT. It should either go all the way in, or stay up, and your left foot has to rest on the "dead pedal."
3. SMOOTHLY LET THE CLUTCH GO UP OR DOWN, TAKING BETWEEN ONE AND TWO SECONDS.
Give this a try for a bit before you go back to smoking the rear tires, etc. You'll probably feel the clutch slow the car down as you let it up during a downshift, but it is probably fine for the car, as most people do it. After a while you can take it to the next step and become Mr Smooth.
Best of luck!
PS: Ask your mechanic to check out the car again, just in case he messed up....