I also think that many SRM players and not just GMs at conventions (in my experience anyway) take into account that everyone at the table is probably at a different experience and power level...
That's obviously not a 100% true statement, as I have run into the other way as well, but in general it seems to be true.
I personally have a character with a high amount of Karma that will have to retire at the end of this season, but I second what was said before - initial build makes a big difference; despite having high karma, he is NOT a min-maxed character. In fact, in the last mission I played last year I got one shotted (not dead-dead, but out)! It was the newer characters with very little karma that actually saved the day and were probably better constructed!